CEL - Cat failure on Bank 1 and 2.

My CEL light came on just after I bought my car. I took it to the shop, they replaced the all O2 sensors and could not fix the problem. The tech told me it wasn't worth fixing and let it go at that. I bought a cheap Tandon diagnostic to look at it myself. Both banks have a max Volt failure that is causing the CEL. I can turn off the CEL, and do it periodically in order to catch any new issues. With the CEL on all the time, I could a catastrophic failure and no real warning to see it coming. I don't like that thought at all. Is it possible to fix this myself without the expense of replacing the Cats? The car runs, but now it is eating gas and I'm only getting 10 - 12 mpg on the highway or driving around town like an old lady (Sorry girls). The exhaust fumes reek of gas and it stinks up the garage for 30 minutes after I've pulled out and closed the garage door. Before the CEL, I was getting 28 mpg on the highway and 21- 23 mpg around town. With the current price of gas, it is putting a dent in my wallet. If replacement is my only option (likely) than I would appreciate it if anyone can help and recommend where I can get the best price from a reputable reseller. Thank you all in advance!

Some good info on a recent thread here . MagnaFlow catalytic converters pass California, fit fairly well, and are half the price of OEM. I bought mine direct from MagnaFlow (“Direct Fit”) Edit: First things first: CEL can be caused by several things. How do you know your catalytic converters are bad? What fault codes are you getting?

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What year and model is your car? Rich

I have a pair of stock cats I would sell from my 01 if you need stockers

If you are getting 10-12 MPG, you have to fix that issue first, then determine if the cats are in need of replacement. sounds like you need to learn how to monitoring your air fuel mixture and then determine the issue and cure it. Don't bring it back to the first shop, they don't sound like they know what they are doing.

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This is the result of the technicians failure description and then I talked with him personally. I had a CEL about a week after I drove it home in SC from Virginia. I brought it in to the local specialist (Porsche) to have it looked at in addition to a radiator flush, oil change, brake fluid flushed and changed, serpentine belt replaced. They troubleshot the issue, replaced the O2 sensors on the CATs and reset the CEL. The light came back on the following day. Another visit to the shop that resulted in the tech saying it wasn't worth replacing them because at the time it would have cost over half what I had paid for the car. The shop is highly rated and recommended with customers from surrounding states bringing in their car to be repaired or more specialized services. A recent post to my question about my key fob not working was a comment from another local for the same shop and I believe I saw his vehicle there as well. Beautiful black model a year or two older than mine. I had gone to another Porsche specialist who recommended I go there as well because he had stopped servicing Porsche's due to burn out from performing IMS replacements. The Tandon doesn't show the actual codes but it will display the status of all the engine and car sensors. It fails on the CAT tests with an error on the Max Voltage readings when the test is run. Not I have not been able to update the software in part because after I registered at the site and registered the purchase, the device failed to show up on my profile and in turn the update software doesn't show the device in order to update it. During my test, I had the option of downloading the codes for vehicles, but choosing Porsche there were no information available. Apparently they are only available on the Porsche Dealership. There may be more high end diagnostics tools available but I just wanted something to perform a check on it and the other cars I owned that are more mundane and have codes. I appreciate the link, I'll take a look and any other recommended alternatives the members recommend.

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1999 Coupe, base model with a few options. Only aftermarket part is a L&N air filter. Other than the error and symptoms describe, there aren't any other issues. The car runs great and is very responsive. Since it's my first Porsche, and have never ridden in another, I don't really have anything to compare the performance with. But you put your foot into it you are driven hard back in the seat. I initially thought it must have a turbo the first time my brother gave me a ride in it and was surprised to find it was just stock. Engine was replaced at 29k for whatever reason, so it has less than 60K on it, well maintained.

Your cheapest tool is probably a durametric: https://www.durametric.com/ You just need a PC to run it. I found on my 99, that when I use my ICON T10 scanner, the data is much easier to understand. I recently posted about my 02 sensors and pictures of graphs, see here: https://rennlist.com/forums/996-foru...o2-sensor.html If you are telling me that you get 10-12 MPG, the car is running extremely rich and you have an issue. I would suggest that it could be O2 sensor related or something else. Once you fix that, you can tackle the cats if you need to. But I wouldn't worry about the cats just yet as you will just harm them if you don't fix the issue.

I would also check the MAF sensor or even replace it and smoke test for vacuum leaks. Addressing these two may solve the CEL problem.

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PM please. I'm interested. Out of curiosity, how long did you use them before switching?

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I'll see if the app can run on a Windows emulator under Linux. I don't have a single Windows based computer in the house and never have.

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I had bought a MAF sensor, but have yet to install it. That was one step I had read about that may be a cause of the CEL problem. I'll be getting the complete service manual for the 996 someone recommended to me in another thread on a question about the electrical system. I have a couple issues I want to troubleshoot that aren't in the service manuals I have. How would I perform a smoke test? If this a tool I can rent at the local auto parts store?

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I hate taking the car to the shop if I can DIY. What type of tools would I need to troubleshoot the issue. Oddly enough the mpg drop came after the visit to the shop.

It's possible the new O2 sensors you received are are functionally worse than your old ones. That would explain the terrible fuel economy and fuel-rich smell from the exhaust. Given that you developed this "10-12 mpg" issue after collecting your car from the shop, this appears to be the most likely issue. Unfortunately, modern parts can be a bit of a crapshoot. I remember reading about another 996 owner who dealt with bad O2 sensors out of the box. Hopefully that shop didn't toss your old O2 sensors, so you can get them installed and see if your fuel economy improves back to its previous state.

You can buy brand new Bosch O2 sensors for $75 each for the one and $55 each for the other. Less than $300. You can change all four in morning by yourself if you've never done it before with some tools from Harbor Freight. You will need a scan tool to monitor. I don't know if a basic USB dongle would work with an app like Torque or not. Get the Bosch units. https://www.rockauto.com/en/catalog/...2)+sensor,5132

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I wish! I have one with 100K miles that hasn�t responded to breaker bar+torch on my bench. Maybe an angle grinder, lol.

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Too late to collect the old sensors. The work was done in September last year. It's been in the shop being repainted until the last three weeks. So they are long gone. I believe another gent in this thread had a link to an issue involving the O2 sensors and steps to troubleshoot the O2 sensors for correct operation by testing each leads voltage. I've got a multi-meter but no jacks or ramp. I need to get a set anyway, so I guess it's time to run around town to find a set (none close to me) and work on that in addition to another issue with the cooling systems and possibility of the resistors on the slow fan gone bad. I'll be getting a Porsche service manual today from Amazon to help assist with other issues I'm running across as well.

To my opinion all the manuals you need are here to download: https://charm.li/Porsche/ The best place for a diagrams for both European and US spec itls this https://ifinterface.com/page/page3.php?lnid=2

Here is the factory manual for .1 and .2. Right click and choose "save target as"

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Hi Paul, No attachments. For whatever reason, when I attach a file without the following steps it never gets attached and posted. I have to select preview post, then attach the files, preview again to verify they are now attached before I submit the reply in order for any attachment/picture to show up in the post.

On an ending note to this thread, I want to check the O2 sensors first. Somewhere I had seen prior to creating this post where someone used a multi-meter to test the O2 sensor. Apparently one wire was supposed to be the ground (0 volt) and the other 3.5 volts or in the neighborhood. I do find it odd that after new 02 sensors were installed that both have the same error with the failure on Max voltage and a pass on the Min voltage. The possibility may exist that they were wired backward (but if it has Min voltage and the sensor only has 2 wires that I am aware of, it seems unlikely), or if the O2 sensors were simply bad from the git-go. If all else fails, then I guess I'll have to cough up for a new set of Cat's (gulp)

Here is a link to the manual: https://audipages.com/911/wsm/

Don't know what your CEL codes are, but many use O2 sensor spacers on the post-cat sensors to eliminate CEL codes P0420/P0430 when running high-flow cats, cat-bypass pipes or if the cats are failing. The spacers move the O2 sensor away from the exhaust flow which reduces its sensitivity. If you google Porsche 996 O2 sensor spacers you will find more info.

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Got those already and another set focused on troubleshooting the known issues. It appears my best bet is to clean/replace the MAF, or the O2 sensors, then the CAT's. I haven't seen anything suggesting the vacuum system has a relation to the problem. Even now, I've not seen the MAF being replaced when they O2 sensors appear to have an internal or electrical failure. But since some information exists replacing the MAF has fixed some issues, it's a dirt cheap fix it has any effect at all on the failure readings I am getting from the cheap Tandon 400 I have. Somehow though I don't see how it would have any relation with Max Volt fails on both banks. But a small step at a time will eventually get me there.

Seems to me most O2 sensors and cat fail due to external causes. Like a failing injector, or burning oil, too rich, etc... The O2 sensors only react to the fumes they sense through the exhaust. The MAF is a start, perhaps check your plugs for burn oil, verifiy your injectors spray, and so forth. The O2 & cat errors are only end results, in my opinion.

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When I bought the car and drove it back 6 hours from Virginia, the CEL light wasn't on. I had made arrangements to take it into the shop to check/replace/change the fluids. The CEL came on two days before the appointment at the shop. The shop replaced the following items the first visit. I wanted to have a complete service done on everything since I had just purchased the car. There wasn't any prior documentation when purchased that existed, so I wanted to be sure the services were done. The radiator and brakes were flushed and new fluid put in. New serpentine belt New spark plugs New fuel injectors Tune up performed. I had to make another appointment to have the CEL looked at. They replaced all 4 O2 sensors but the CEL light stayed on. Today I am replacing the MAF. I'd done a little bit of research on YouTube just after the shop threw up their hands and the MAF was named as a culprit in one or two other than ones on how to replace them. I'm keeping my fingers crossed. You know the silly thing about replacing the MAF? The Bentley service manual has exactly 1 page on it, and it's only about disconnecting the electrical connection. The service manual from Charm doesn't have a single mention other than a sensor named Air Flow Sensor/Relay that appears 8 times in the troubleshooting and parts sections. The WSM PDF's don't have a single mention. Wayne Dempsey's 101 Projects book and his Pelican Parts do. I prefer the hard copy for my aging memory cells and the sensual luxury of getting my greasy fingerprints all over it Beats carrying my tablet out to the garage to reference the web site.

What are your CEL codes? It may be as simple as adding post cat sensor spacers like many of us do to run 200 cell cats.

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I borrowed a better reader and I'm getting a P0140 and P117. O2 sensor voltage over spec and over heating. I looked at the MAF yesterday, Found the screws loose and a sealant over the O ring and into the body. I cleaned that up and put it back in, then tightened the screws hand tight. I reset the codes, then went out and wrung out the engine down the Interstate at 75 mph in 3rd gear while running the rpm a tad over 5k the entire time. The light stayed off. This morning, it came back on. I purchased a new MAF when the CEL came on and put it on. It failed on the EVAP this time with the other failures that had already been reported. The old one went back and the error went away. Tossed the new one in the trash. So I'm on to the next step. I'm going to run a smoke test to check the vacuum hoses before moving onto the rear O2 sensors that are failing before resorting to replacing the CAT's. I don't want to put them and have the error still come up. Where would be the best place to find the 200 cell CAT's you are referring too and the best part to look for. I'd certainly go with that option if I have to replace them. I don't expect them to add any real performance, just work Any other areas you can suggest to look at that could possibly cause the errors?

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I would slow down and not throw anything away. Make sure whatever parts you buy are from top notch manufacturers. Especially a brand new MAF. You have two 02 sensors. Pre and post cat. Its the post cat that reads the fumes. This is where people add the 02 sensor spacer. Google 02 sensor spacer for Porsche 996. You will see every cat manufacturer has them because many 200 cell cats will need them. Fabspeed, FVD, and probably Soul will have them. They come in straight and 90 degree angles depending on the shape you need to fit. The spacers trick the sensors into thinking you dont have a problem. You have alot of issues you are dealing with on your 996 as you refresh it. One of which is trying not to replace a set of cats that are old. The spacers may help. They are inexpensive and you will eventually need them if you go with 200 cell cats.

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I'll give the spacers a shot. It can't hurt to tray. It sure beats replacing the O2 sensors and still not fixing the problem, much less forking over the bucks for a pair of CAT's that still may not fix the problem. Thank you!

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​​​​​the spacers will do nothing to help if your 02 sensors are shot.

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FWIW our catted products don't come with O2 spacers, it is very rare for someone to have a CEL with our products. We took a lot of time to find optimal cat cores and wash coatings to support long term CEL prevention on our high fow catted setups. The exceptions I've seen to this on the M96/97 platform are engines with excessive blowby (typically bore scoring), bad or ethanol rich gas, and excessive idling under warm up conditions. Either of these variables can throw off emissions readings enough, even temporarily, with high flow cats to pop a 420/430 code even though the cores and wash coat are in good condition. We typically don't recommend O2 spacers as a solution to cat codes unless the cat cores have been inspected prior to install. It is common on these models for the factory cores to break and dislodge from the outer shell. These pieces can rotate and clog the exhaust, and also get stuck in the mufflers downstream, which can be damaging. If the cores have been scoped/inspected and no visual deteriation has been found, then it could be the wash coat was damaged/worn out over time, or the the vehicle condition/fuel/driving conditions aren't optimal and a spacer could be a consideration to bring readings back in specification. This is different from car to car, there is no spacer that will "work" right out the gate. If it is not restrictive enough to get in the parameters your specific conditions need, it will continue to throw a CEL for catalyst inefficiency. If it is too restrictive and bypasses the parameters you'll throw an O2 sensor CEL for slow response, signal implausible, and/or lean/rich condition. If you're in an emissions free area, we recommend ECU tuning (Softronic) for a conclusive resolution to those codes. If you don't want to deal with potential O2 spacer adventures, ECU tuning, or the factory cats are deteriorated to the point of replacement...we do have quality upgrades available via our factory crossover style sport cats and X-Pipe version. https://soulpp.com/product/porsche-9...ic-converters/ https://soulpp.com/product/996-carrera-soul-x-pipe/ Regards, John Gaydos

To the OP: didn't you say you have a K&N air filter? Is it in the stock airbox or is it the K&N kit? Are you using an oiled air filter? That will drive your MAF sensor to read wrong.

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They were replaced roughly a month ago. I can test if they are still good. There's a couple paragraphs in the 101 Projects book that outline a simple test. Both the lean and rich cycles are run and the car should run accordingly. I'll run the test before I add the spacer. If it fails to run both rich and lean modes, it will need to be replaced. I'm hoping it's simple fix vs the expense that awaits. Otherwise I know I will have to replace them. It's quite possible they have burned out. My MFA passed it's test, next I will rent a smoke machine and see it couple possibly a leaking vacuum line effecting it. I don''t know, I'm not sure, but I need to approach all this in a logical manner and use all the information available to me. The O2 sensor is the only fault being returned. I really don't want to go any further. I've priced the CAT's and grimaced. If the sensors are still good, the space would be next. The reader report may point to both the O2 and the CAT's, but in all likelihood the sensors are causing the failure being out of spec on the back end of the CAT. I have my fingers crossed. I want this fixed as soon as practical, but delivery times may interfere with the speed it can be fixed.

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This above 'Tune up performed' could be an issue... What was done related to the tune up?

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I'm sorry, I misspoke. I meant to say they checked the tuning. They didn't mention any changes (none noted on the invoice) to it and I didn't ask for anything special to be done. I assume it is factory spec. It's the highest recommended Porsche shop in town. Another local forum member also highly recommends it. I sincerely doubt they did other than check it. The shops entire parking lot is filled with various makes and models of Porsche with about a third to half in the lot are out of state. Usually with NC, TN and even a FL plate one time I was there. The shop isn't in a big facility and can only do so much work a day so there is a backlog to the garage in addition to those waiting on parts. If people are traveling out of state to have their car serviced, and willing to wait however long it takes, tends to give impression the shop is above average to me. It doesn't strike me that they are incompetent or careless. But I think they weren't thinking out of the box right after replacing all four O2 sensors. It's possible they just assumed the continued failure had to be the catalytic converters on a car with 92k on it. The engine was replaced though at roughly 30k, so it only has around 60k on it. A bit early for a failure, although there is still a small percentage failure among all the manufacturers each year. I know it happens. I had one fail on me around 17k miles with the vehicle I purchased new about 18 months earlier. The car only has one symptom. It's running rich and none of other symptoms that also indicate a bad sensor causes. Starts just fine, no chugging, stuttering, acceleration. or poor performance. All common symptoms of a bad OS2 from what I've read.

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I am. But the MAF just downstream of the filter midway to the intake is 5 years old and clean as a whistle, just like it just replaced, but it was replaced in 2019. So apparently the filter has never been oversaturated at any point since then. I had heard the MAF could cause a CEL. So I did look at it, The MAF housing was a little loose where it sat, maybe a 3/4 turn lose before it would need to be hand tightened. I removed it, inspected it, but the only thing I visible was what appeared to be remnants of a sealant applied to the O ring and a little bit sticking on the sides just below it. Didn't see or feel any residue or oily feeling to suggest the sensors could be coated. I cleaned the O ring and inside, tightened the screws lightly hand tight. Reset the CEL and took it for a drive. The CEL came back the next morning. I had a new unused spare on hand, so I swapped them out. Drove it with the same result. So I put the original back. The post O2 errors still occurred with the new one. I may need the spare in the future, but not in this case. I think I have ruled out all the possible error conditions that could occur, so I'm down to address the sensor problem directly.

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Of course, if they fail then next is replacing the sensors. Just because they were changed a month ago means both couldn't be bad or go bad a few miles down the road after they were changed. I did my due diligence. I the car back to have it retested, but they said both the catalytic converters were bad and needed replaced. Their recommended solution was just to continue to just continue to drive it. I can statically test the post sensors from the wiring interface checking the sensors response. I would still give them a shot. I have to order the spacers and wait for deliver. I can buy sensors locally from either an auto shop that has them on hand. AutoZone southeastern distribution center is located here, so the part could be delivered the next morning. All else fails, the dealers only 15 minutes down the road. Only OEM Bosch sensors. No aftermarket parts. if this doesn't resolve the issue, then the only option remaining is to bite the bullet, break open the wallet, and replace the CATs. The spacers, new sensors are still cost less than the converter. It's worth the expense, time and effort to try both alternatives before throwing in the towel. I'm ready to pay what it takes to get this CEL gone.

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You wouldn't know off hand if I need a 90, 45 degree, or straight spacer would you? I'm not in a position to take a look on the understand quite yet. So I would appreciate it if you can point me to the right one.

O2-sensor spacers merely mask a problem they don't solve it. Ask if thr shop has a stand-alone wide band O2 -sensor, including controller and gauge/display. If yes, have them put it in place of the pre-cat sensor on one bank and then the other. That will show you how the car runs open-loop. At partial load and 2.5k rpm it should be close to 14.7 AFR aka lambda=1. Ideally they have a wide band set-up that can mimic a narrow-band sensor amd feed that signal into the lambda sensor connector on loom-side.

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They were on the car about 80K miles. IM if you are interested.

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I dont remember with oem cats. It all depends on the available space to match with the spacer design. @hardtailer said it best. The spacers may help to mask the issue, but if your cats are toast, you will have to eventually replace them with a used set or new set. FWIW, make sure you keep your oil fresh until you fix your MAF/fuel injector/02 sensor/Cat problem. Too much fuel in the cylinders doesnt help your bores.

Im pretty sure u need the 90* spacers.

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I understand what you're saying. Both sides failing at the same time is not a normal issue. I change my oil every 5k. I've been doing that for 21 year's and the benefits. Both banks having the same failure, at the same time is not normal. You usually only have an issue with one side. So the issue feels unusual to me. I've tested the MAF. The current unit appeared as clean as it was when replaced in '19. I had a new replacement on hand to swap out, but resetting the error codes to turn the CEL off didn't stop the error returning the following day. I did a smoke test this morning without any indication of leaks. Any upstream issue with the wiring would have to an over voltage situation, but both sensors never come together and an over voltage condition would result in a blown fuse. I'm not ruling that out. I'll be looking into the fuses right after this post and emptying the garbage.

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Viewing the pictures accompanying the sensor replacement project in the 101 projects book and in the Bentley service manual, You would be correct. So I bought a set of 90* spacers from Technodyne to try and see if will fix the CEL. I also bought one sensor to swap out before the spacers are installed to test if there is truly an issue with the new sensors (all 4) installed a month ago trying to fix the CEL (it didn't). Troubleshooting all the areas, much less identifying on my own, then with the suggestions in this forum have greatly narrowed the areas to take a look see at.(to include your own input)

@dglenn99 I sent you a PM. This sounds like maybe the previous owner reset all the CEL faults before you bought the car. It takes time/miles for the CEL to re-register. This happened to me. Anyway, I would suggest you get a better diagnostic tool, like a Durametric, or have a Porsche tech run the diagnostics with a professional unit, which would indicate more details. At this point, throwing parts at the issue will get expensive, if not frustrating, quickly. Also, you might consider replacing your air filter with an OEM one; the reusable K&N filters are known for letting fine particles into the intake, can be seen in used oil analysis as increased silicon content (I.e., sand).

If the OP has not purchase a tool to monitor O2 output, you are just chasing your tail. This should not be hard to troubleshoot and repair. $0.02

In all this theorizing the only codes you post are P0140 which is "no activity from Bank 1 Sensor 2 " and that has NOTHING to do with Catalytic Convertors...( the Cats would have to be working too well/efficient to flat-line the voltage signal ) And you post a code P117 which is NOT a valid code. Double Check the codes. and start over from the beginning ... ............. ( I think that is the only way you will EVER get to the bottom of this )

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Based on this post Gemini said: Focus on the ** P0117 ** code first, as any cooling system anomaly on an M96 engine is a high-stakes issue that can lead to cracked cylinder heads or bore scoring if ignored. While the ** P0140 ** likely points to a dead post-cat O2 sensor or a heat-damaged wiring harness�a common nuisance on 996s�the temperature fault suggests the DME is seeing an "out of range" signal that could either be a failing sensor or a genuine thermal event. I recommend inspecting the coolant expansion tank for leaks and verifying the engine ground strap, as erratic voltage readings across multiple circuits often stem from a corroded ground rather than simultaneous sensor failures.

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I'll take a look at the K&N issues. I'm not good with lifetime air filters. Don't believe in using them. That said, the OEM filter box is long gone. My brother (previous owner for 10 years) said he had not had a CEL since '19 on it and the MAF was changed along with all the electrical control boxes. I forgot the reason these were replaced, but all of this was covered bu his insurance he said. I drove 300+ miles home and the CEL didn't come on for a couple days. He does have a ODBC reader, nor mechanically inclined except for oil changes and brake pads and I taught him to change both drum and the current system (name escapes me at the moment. Senior disease ...) pads several years ago, and is the sum total of his abilities. He had also just moved to the area a couple months and is unlikely made enough new friends where he might have access to one. In addition there isn't an auto parts store that will do more than check, or car shop that is fine with running diagnostics, but will want to fix rather than just reset the CEL. These are my thoughts on that. Although I've ordered the sensors, I was viewing the wiring diagrams to see if there was a possible electrical problem that could effect both sensors reading bad, even after all 4 had just been replaced (OEM) on the car in an attempt to fix the system. I just discovered a relay on the Post Distributor Bridge Plug diagram at position 5 with designation 21/1 and 21/2 that input the post 02 sensors containing 4 pins (2 from each post sensor heating circuit in the O2 sensor.) I don't yet know where this board is located in the car. The 30 Amp fuse in the fuse box, C2 tests good so it's not a blown fuse problem (Although I found 2 blown fuses and 4 missing fuses. I didn't have anything written down on the position of the blow use so I don't know what purposed they` served. Since both fuses are a brighter color than the existing fuses I might be able to locate them.)

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No theorizing here. I didn't type it in correctly. It's P1117, or an O2 heating element failure with the P0140 error reporting it wasn't receiving data from the sensor. I think the P1117 error is related to the P0140 error being unable to receive or send any data. No scatterbrained purchasing either. I'm following a proven strict and holistic set of steps to approach the problem. I'd only had the car two weeks before I made an appointment with the local shop to fix the CEL. They replaced all 4 sensors in the attempt to fix it, then threw up their hands when they couldn't. They said it would be too expensive to follow up. The only thing I knew then about the car was how to drive it. Since then I found this forum and some others where there are a plethora of experienced and knowledgeable people to answer my somewhat inane questions on other areas I need to address on the car. On this subject, the answers have become variations in the same theme. Replace this or that. I call this information conventional wisdom. This usually results in a fix 95%+ of the time. The question I have has now evolved into: What can cause both sensors to fail, with the same error codes, on both banks with the post converter sensors. Does a single point of failure exist? From the books I have, the free service manual information from the Internet and the forum input, only answers based on the conventional wisdom exist. Time now to shift to thinking outside the box. Now I have a theory. After digging through the wiring diagrams past the O2 sensor cables to the relays. Bingo, I have a hit based the wiring diagrams from the WSM manuals, Wiring.pdf, Sheet 24, Sheet 24 - Relay Support #1, Relay Support #2 on Page 97-99. Looking at Relay Support #2, finding the relay at Plug position # 6 has two inputs for the 4 wire input from both post O2 sensors and with 1 output pin. These the incoming relay ports are also named. 21/1 and BS. 21/2. If the relay is closed, sensor input would not pass through to the output. Thus the error 'no data is received' P0140 error. This would cascade down to the heater not sending it's data that may be the cause of the P1117 'Heater overheating' verbiage. This falls in the remaining 5% conventional wisdom won't fix

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I got the error code wrong. It's actually P1117 relating to sensor overheating on the post cat sensor readings. I think I have an answer to the problem posted below. BTW, I've checked the harness for burns and cuts in the wiring harness on the sensors. They are good, no blemishing or other obvious possible areas of damage.

I think these relays are at the back inside the cabin under the carpet. You are getting errors only on one side/bank of the engine so in your case I would swap the postcat sensors and see if the error moves to the other side...

The sensors are heated until the are at operating temps, this is to get them to operate quickly after engine start. Decades ago heating was not common and they were heated by the exhaust gas only (all single wire lamda sensors). You can delete the fault, pull the relais that supplies power to heat the sensors ensure that the sensor's output still reaches the DME and then drive. If the p1117 returns, you have too high exhaust gas temps, which can be caused by: -lean mixture during combustion. ask AI at what temperature p1117 is set and if exhaust gas can become that hot through lean mixture. A standalone wideband lambda sensor with display would allow you/shop to observe this. Error codes would hint at lambda sensor signal being out of range/spec, which is often mistaken for the sensor itself being faulty, even by professionals. -excess fuel and enough oxygen, where the fuel burns inside the cat, heating it and the lambda sensor excessively. You would see accompanying error codes of misfires in this scenario. -far fetched but perhaps fuel additives that 'clean' by raising combustion temperature contribute to 1 and/or 2. If the code p1117 does not return, then obviously something is wrong with the heater circuit, of which I have no precise knowledge. I would guess it's either a PTC heating element that is constantly supplied with 12V (basic method) or the DME switches the relais for a fixed time frame or, yet another possibility (overengineered), the DME monitors temp via current through the heater element to heat until operating temp has been reached. If it doesn't stop heating, then sensor gets too hot and p1117 is set. I would suspect relais first, DME not very likely. If this is too analytical for you or the shop, then use a smoke machine to find air leaks and have the injectors tested and cleaned or replaced with new ones altogether.

What I mean by theorizing is all the talk about Catalytic Convertors, cost, new and used, brands, and the "spacers" that have small Cats in them ti mimic real Cats when nothing points to Cats and assuuing there is issue on "both sides", The codes P0140 and P1117 all point to Bank 1 Sensor 2 circuit... Just trying to stop you from barking up the wrong tree and spending thousands on Cats and Spacers just to have the same problem... There are only 4 wires on that circuit that need to be verified that they are wired correctly, not broken, not shorted to ground, not shorted to each other.....Tested end to end if they are OK then the issue is in the DME.. the O2 Senor does have a relay and a fuse sending 12v when engine is running, but the ground side resistance is controlled by the DME at 256 ohms, 128ohms, 63ohms ect, to control the temperature... This resistance can be read by using PIWIS and also watch the O2 Sensor voltage bounce from high to low voltage with AFR... Also while I don't blame the reputable Shop from replacing all 4 O2 Sensors, at 25 years and 100k miles they are aged and lazy to respond, but I am disappointed to hear they throw up their hands and say the car is not worth it.... If you are willing to pay the cost, they should be willing to put out the time and effort to fix the problem.... BTW : if it turns out that the DME is the problem, ECU Doctors can probably fix it, or at least supply a used DME and marry it to your car, Immo and Keys...

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Thank you for a location. I'll know in a few days if I am right or wrong.

The possibility may exist that they were wired backward (but if it has Min voltage and the sensor only has 2 wires that I am aware of, it seems unlikely), This might have already been discussed , but if you in fact have two wire sensors that would be a problem. that first paragraph is a quote cut from thread number 21, written by op.

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I appreciate your concern on the money side. I've been looking for anything that would stick to the wall. I'm finding my options are becoming more and more limited in scope. Your previous comment on the sensors connecting directly to the DME had me go through the Sheet 24 on Relay Support 1, Relay Support 2 information, with Sheet 12 covering the DME 5.2 Engine, Fuel, Ignition System wiring diagram. This was a great help checking what may lie between the DME and the sensor harnesses. I made a list, and checked it twice Although there are some sections that routed through Relay Support 2, Relay Plug #6, It only contains two bus connectors that connect two different source Pin #'s of which the Ground went to the DME and the other to the Injection Relay Ignition and Oxygen Sensors on Pin #3. I ruled out the post-cat sensors being part of the problem. The sensors come with the harness and connector. There wasn't any mention of sensor harness issues on the old sensors and the shop is competent enough to ensure the new sensor harnesses were tied up and out of the way of burning or cuts from it swinging into the chassis or dragging along the road. Think about it, the odds of replacing all 4 sensors, and only the Post-Cat sensors display identical error codes that came on simultaneously just moments after they were installed don't make a lot of sense in that 4 sensors were replaced, but half of them bad, and both are on post-cat Bank 1 and 2. So I pass. Currently I've only got $55 of skin in the game to date. Maybe the spacers will cause the CEL to stay off, or not. At this point I really doubt it. I bet the CEL will come back. Won't know until I try. I bought them before I began digging into the wiring. This leaves me looking at either replacing the Cats ($4k+) or the Relay Support 2 harness. If a rat ate the O2 sensor wiring, I hope it's something I can repair/rebuild. Otherwise I'm looking at $2.1k for a harness connecting to the circuit board. No doubt it will have connectors from each component that will require it be reconnected to the other components involved on the Relay circuit. I recently had back surgery for the second time and I don't want to loose the ability to walk again. So other than repairing it (which I can do at my own pace without digging around with all the connectors), it would mean a trip to the dealer and a boatload for the labor in addition to the harness cost. I think the DME being a problem is somewhat unlikely. in 1998 multilayered circuits could create a monolithic single board that is hard to damage or have errors in the circuits without effecting other areas. For instance the ground pin from the sensors would also connect to all the other grounds in other circuits on the board into a single connector for the board ground connection. I've rarely seen a problem. Since monolithic boards came on the scene, 98% of problems will be in the software/firmware, and only 2% hardware problems. (IMHO) I won't toss rule it out. If all the connections have continuity, then it would be time to take a look at it. Here is the skinny on the DME connections after all the time the research took. The 2 sections that I term 'Indirect' is when 2 connections connect in a terminal with only 1 output to the DME. And the Ground combining all the Pre and Post CAT Ground leads go through Bus 21/2 with 1 connection to the DME. Semantics, yup. And one section uses Bus 21/1 and skips the DME entirely that would result in the car ignition not working. Bus 21/2 is the only one that could be cause the these error with multiple ground outputs into a single pin on the DME. Direct DME Connections: Post-Cat Sensor Bank-1 Pin #4 Connects directly to DME Pin# 77 (labeled: Signal Oxygen Sensor Bank-1 Post-Cat) Post-Cat Sensor Bank-2 Pin #4 Connects directly to DME Pin #76 (labeled: Signal Oxygen Sensor Bank-2 Post-Cat) Pre-Cat Sensor Bank-1 Pin #4 Connects directly to DME Pin# 79 (labeled: Signal Oxygen Sensor Pre-Cat Bank-1) Pre-Cat Sensor Bank-2 Pin #4 Connects directly to DME Pin #78 (labeled: Signal Oxygen Sensor Pre-Cat Bank-2) Indirect DME connections Post-Cat Sensor Bank-1, Post-Cat Sensor Bank-2 Pin #2 Combines on Terminal 32 then connect to DME Pin #1 (labeled: Heater O2 Sensor Pre-Cat) Pre-Cat Sensor Bank-1, Pre-Cat Sensor Bank-2 Pin #2 Combine on Terminal 32 then connect to DME Pin #30 (labeled: Heater O2 Sensor Post-Cat) Indirect Ground Connections to DME Pre-Cat Sensors on Bank-1 and Bank-2 Pin #3 Combine on Terminal 33, then connect to Relay Support 2 board, Relay Plug #6, Bus 21/2 Post-Cat Sensors on Bank-1 and Bank-2 Pin #3 Combine on Terminal 34 then connect to Relay Support 2 board, Relay Plug #6, Bus 21/2 Relay Support 2 board, Relay Plug #6, Bus 21/2 connects to DME Pin #46 (labeled: Ground O2 Sensors) No Connection to DME Connection to the Injection Relay Ignition and Oxygen Sensors Pre-Cat Sensor Bank-1, Pre-Cat Sensor Bank-2, Post-Cat Sensor Bank-1, Pin #1 Connects to the Relay Support 2 board, Relay Plug 6, Bus 21/1 Relay Support 2 board, Relay Plug #6, Bus 21/1 connects to the Injection Relay Ignition and Oxygen Sensors on Pin #3

Why do you keep saying "BOTH" post cat sensor are bad ?? You have only posted 2 codes .P0140 and P1117 and these two codes point to bank 1 Sensor 2 ONLY !!! Unless you have seen other codes that you just have not posted.....??? You need to follow my advice and test the 4 wires to that one sensor end -to-end.........

If you haven't purchased a scanner yet, now is the time to do it. You'll thank yourself later.

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(!Groan!) Shows what I know about 'newer' cars. If it ain't got weber carbs, uses a timing light and a grease gun for the suspension, you get the idea. No wonder you were getting rather irate at me, and I can't blame you a bit I didn't know there would be different codes for each bank, I just assumed and relearned the meaning (Making an A** of U and Me as the Drill Sgt told me while I was visiting for 13 weeks at Parris Island) So the full code rendering is: P1117 - Post-Cat O2 sensor Heater Bank-1 P0140 - Post-Cat Sensor Bank-1 No activity detected P1121 - Post-Cat O2 sensor Heater Bank-2 (Although it's not listed in the Bentley Manual, it was online) P0160 - Post Sensor Bank-2 No activity detected I'd love to test the wiring harnesses last week, but I don't have a set of jack stands and the only jack is the OEM jack the car came with. I'm not sticking my head under it until Thursday when that is no longer an issue. Big snafu over the fund transfer and having to refile the paperwork. Now that you see the actual codes, you can better understand my reasoning the whole time. It wasn't until you pointed out the specifics of the original codes I'd posted, I couldn't understand why I was making myself clear. Sorry, I didn't mean to give you heartburn. Thank you for your patience.

Yes the codes are Bank specific and also Sensor specific and the 2 extra codes ( P0160/P1121) CHANGES EVERYTHING......We are on the same page now... I would concentrate on the Heater Circuit......Those two post cat Sensors share the same circuit up until a Splice inside the wire harness ..

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Good call. I should have noticed that while I was cruising through the wiring diagrams and writing the connections down that I posted. Forest for the trees error. I was more interested in proving you wrong about all the cats connecting directly to the DME. The diagram symbols are totally unfamiliar to me, which made things a bit dicey, but I know it had seen something in the middle. Then I realized what the BS had to stand for and that put a hole in my balloon and I deflated.I had to be satisfied with the one connection to Ignition circuit as childish as that was. I'll give that a go. It appears to be exactly what I was searching for. The odds of this occurring in this manner were enormous. I just had a very strong feeling conventional wisdom of replacing the sensors, then moving onto sensors, then the cats wasn't going to be a fix this. It just too unique to occur often enough there was an existing solution. That's when I went stepped out of the box and began looking elsewhere and anywhere that touched the cats that was possible to generate the condition, so I started climbing upstream. I don't doubt you have nailed it. Now to just get a pair of jack stands and a jack that will slide under the car and safely lift it. I am very dubious of using the jack for use on the tires. It will be later this week, Thursday or Friday. Then I'll post the result. Currently, with only 16 mpg, I could literally watch the gas gauge drop as I was driving. I'd love to get the 5 mpg back I'm capable of getting around town. I've always been able to exceed the EPA figures. The answers I got posting the question about getting more mileage out the car in town will help me find the sweet spot I know exist. And I'll have fun the whole way. I love this car. Thank you for all your help and advice even though I drove you crazy up until the post. My insistence that both post-cats were having the same errors when the codes I had didn't match what I was saying. That had to make you feel I was out in the field sitting under a shade tree drinking electric outlaid disconnected to reality without a clue as to what I was doing. Well, I still don't have a clue

Ow, unfortunately I have no idea where the O2 sensors connect to the upstream wiring harness. I've got the car jacked up and inside Support Relay 1 and the DME are available to do testing. I've got the multimeter and a 22 gauge wire to extend a lead from the engine compartment around the outside to the DME test point. One side note. When I opened the compartment with the relay and DME, I found what appeared to a mouse nest under the relay box (Not the DME). I visually inspected the wiring connecting both units but I did not find any sign of the sheath on the wiring had been exposed. I may find the fault is buried between the DME Pin #! is located where the wiring passes through the to the O2 connection. I'm not sure I can fix it if it is occurring there or manually run a new wire and splice it to substitute it the original OEM wiring scheme. I'd appreciate it if someone can point me in the right direction. Thank you!

Lots of places for a Rat to sit and chew on the wiring.... Test the affected wires at each end to confirm the Rat has chewed it into ... The Professional way to repair is to remove the wire harness and repair the damage... The Shade-Tree way to repair is to just run a jumper wire near the ends and jump the damaged area... The wiring harness for the O2 Sensors runs across to the left side then through the firewall down the left inner fender under the Coolant Reservoir then across the back under the engine lid latch... I remember back 20+ years ago I had a fairly new one that a German Shepard had chewed up the left rear quarter panel and ripped the back bumper off....After it got out of the Body Shop to repair that damage the CEL was ON and they sent it to me...I tested the wiring and confirmed the open circuit in the O2 Sensor wiring. So I removed the rear wiring harness and found where a RAT had sat behind the Coolant Reservoir near the firewall and chewed the wiring into....I repaired the damaged wiring .. I heard that the owner was going to have the German Shepard put down due to eating up his new 911, but I called him and told him it was the Rats fault, The Dog was just trying to stop the Rat from eating on the wiring......lol Good luck with the repair, i think you now know what to do ...

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My O2 sockets were in two different places. Drivers side, 4 in left of the serpentine belt just under the latch while the passenger side had it against the right fender. It was good run, but I had continuity on all the lines, between sensors, then both to the DME. With the O2 plugs out, I went ahead and tested the heater output. Values in millivolts sure isn't the anticipated variance between .1v and .9v while the engine was running. The odds on this happening were enough for me to waste a lot of time going back and forth. It really chaffs my rear. Nonetheless $250 or so for new ones still beats replacing the cats. Since I just bought a floor jack and stands I'll do the swap myself. I still keep kicking myself in the butt, but I'd never found the mice nest if I hadn't gone this route. I closely inspected at all the wiring harnesses but didn't see any visible areas of damage from my point of view. I may find myself revisiting the area again since I've had a few issues that may still be related to the wiring. No rest for the weary. Again, thank you for your help and patience with the stubborn newbie. I appreciate it. Dang, I hate to be wrong Now I know how to pull the connectors on the boxes back there and test the O2 sensors in the back.

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Wouldn't you know, I tested the wrong two connections, signal and ground to the DME Just in case I was wrong the first time, I went back to the Internet only to discover to my chagrin, it's the two WHITE wires (head hanging low) With this new information, I tested between the leads on the O2 sensor side, #4 correctly had a 2 ohm reading while # 3 being the ground, continuity ground (on both sensors). BUT, with ignition on, I tested the upstream plugs to the DME. 0v vs 12v on #4, and #3 showed no continuity. (on both sensors) Onto the DME and testing pins #77, #76 for 12v and #46 for continuity to ground. Actually, I can skip the ground test since it would have an effect on every unit connected to the DME. I'm willing to be that both #77 & #76 will both have 12v Then it's to where freaking mouse may have found a delicacy. While it is still possible there may be a short due to rubbing somewhere on the chassis, I find it doubtful. This would be more common and there would be chatter on the Internet or even the forum members experiencing it. Not a large number, but enough to trigger a search engine algorithm. Not looking forward to tracing the harnesses.

Its not hard to get to the wires. Remove the rear seat unbolt seat belt remove shelf pad and rear side panel Remove sound deadning foam unhook rear tail light and o2 sensors in engine bay Pull on harness and grommet from inside and pull the harness into the car U wIll be able to inspect all the wires

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I read somewhere that clothes drier sheets are a natural smell repellant for mice. Mice are small and can get nearly anywhere. Rats are bigger, so don't know repellant for rats? I just put them under the frunk plastic cover parts and here and there in the car/engine area. YMMV

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I have continuity between Pin #1 on both the pre and post sensors, but then it passes through to Pin #5 on the Ignition and O2 sensor relay. This circuit doesn't connect to the DME. I have ruled this one out for the moment because I am getting errors on the upstream heater circuit wiring. I have continuity between both post sensors on Pin #2 between the splice and DME Pin #1. I have continuity on Pin #3 between both post sensors up to the splice, but not to the DME (Pin #46) Both sensor Pin #4 connect directly to the DME and I've not tested continuity on those yet. Pin #3 acts as a ground while Pin #4 carries the signal and the signal from both sensors. Pin #4 on both sensors are independent of each other connecting to DME Pins #76 and #77. These two pins are supposed to carry 12v each from the DME to the heaters and return to ground on Pin #3 With the ignition on, both of the sensors Pin #4 don''t have the expected 12v output and Pin# 3 (ground) is open. If all 3 wires have connectivity from the O2 upstream connector to the DME plug, then it means the DME is the source of the CEL and needs replaced. At the moment, none of the harnesses exhibit any sign of damage where the mouse nest was found. Neither the DME or Relay Support board 2 connectors have any visible damage as well. So far I am considering myself very lucky. With the number of cats roaming the neighborhood, mice and other rodents are scarce compared to the barn my brother had the car stored in the previous 5 years. I'm still going to leave some poison in that compartment for the future rather than just crossing my fingers and hoping for the best. My last run-in with a mouse/rat was in '92. We were having network problems in the warehouse due to wires being chewed on in the wall and I had to fix it. After the wiring was on the verge of being too short to connect to each other, I resorted to putting poison in the wall. No more damage from that point on. But, the mouse/rat had the last laugh. It died in the ceiling above my parts closet and stunk to high heaven for a couple months. Not too long afterwards the wiring manufacturers switched the wiring compound so it no longer attracted mice.

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I've not heard of that particular trick. I am too enamored with putting rat poison in the cabin. Frunk, not an issue, but I don't want to be breathing it inside. So I'll take a look see at your alternatives.

Except everything could still be fine. As in my car there was no issue with the dme and the wires were fine to the dme. The issues i had were the pins were spread in the dme plug and the pins were not touching the plug spade. It took inspection with magnifing glasses to see it. Also when testing the dme plugs always back pin the plug, do not stab the front if the plug. Before u spend a small fortune u can do one 2 things. 1. Take the car to a dealer that has a break out box and they can interup the harness at the dme and test both sides. 2. send the dme, immo and key to ecudoctors and let them test the components. i still think its in the harness and if u dont have continuity on everything on the drivers side and u can not inspect the harness fully without pulling the harness back into the cab. The coolant tank blocks your view and mice really like it back in that corner.

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All the wiring checks out, O2 sensors good. Bottom line: replaced the Catalytic converters

So after all that, I assume the new cats corrected the problem? Did the cats show any signs of coming apart?

So, bad cats with no cat fault codes... Your cats must have found a "new way to fail"....lol ( one that even the Porsche Engineers didn't count on )

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I simply don't know. The cats I ordered won't fit so they are going back. The wiring is good. Hate to admit it, but I measured the lines to the DME backwards. So everything is good there. At this point I'm ready to take it to the dealer. I've read somewhere it could be possible if it's getting too rich of the fuel air percentage. It does smell strongly of unburnt fuel (raw gas smell) at idle and hot. I'm out of patience with my attempts, so it's time to bite the bullet once another shop finishes the wheel bearing, shocks and suspension rebuilds in an addition to the rear axles. Apparently they are tossing out grease in the area. I don't need the tranny or engine damaged beyond the current CEL issue. It's been a tremendous drag at 16 mpg on average. I did manage to get 18 this week with a spirited drive to the mountains and some highway miles to and fro. It's time to get a PWIS hooked up and the the problem addressed once and for all. My DIY attempts have gone as far as I get. I'm just hoping I don't get burnt. I went in recently to them to get the wheel lock bolts measured to get my wheels off to perform the current services and they got it wrong. I was lucky to discover the original. That didn't fill me with any confidence in the dealers shop at all.

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I misspoke about the cats being replaced just yet. My bad. I'm tossing up my hands and will take it to the dealer when the current service work is done next week. I'll post the results when it's fixed. All my DIY attempts have failed. I want to leave a another solution to this issue on the table.

Too much fuel is being injected, that we can safely say based on all of the above. If you're already in doubt about the shop, don't take it there. Consider firing the parts cannon at it, if you feel confident at R&R'ing but be aware you can make mistakes that just worsen this whole ordeal. Replace in this order (of accessibility) --MAF, if not done yet (i didn't re-read all 6 pages). Make sure return fuel line is unobstructed -coolant temp sensor that provides input to the ECU. Be aware it is a different one than the one feeding the instrument cluster. -replace FPR and all six fuel injectors. -Replace all seals you get access to on your way to the injectors. Parts cost will be offset by the labour cost saved. Or, find a shop that is known for solving the difficult cases of fueling issues, irrespective of brand. ‐-------- Edit, after reading the whole thread again. Summarizing, your car has 2 issues: 1.abnormally high fuel consumption 2.CEL on post-cat O2-sensor You seem very much focused on nr 2 whereas nr 1 is far more serious in its potential to further harm your engine and cats. (Change the oil now, don't drive it till you reach 5k on this fill as it is bound to be diluted with fuel by now!) New MAF made no difference but the fresh o-ring on the new MAF is reason enough to have kept it fitted...) nor did the new injectors (have you been shown the shiny new plastic injector bodies so you can be sure that indeed they have been fitted?). That leaves a defective FPR (diaphragm torn and dumping fuel into the intake via its vacuum hose) and/or Intake air temp sensor + wiring as possible causes for overfueling that have not been checked. If you prefer to increase the chance of succes DIY'ing with the help of those responding to your posts, I suggest you to take a specific question or description of next diagnostics step in a reply as a 'to do' and report back what you found. Nothing more, nothing less. Also, proof read before posting! Those who know what they are talking about (not obvious immediately who they are, I understand that) in this thread will interpret the result you got and tell you what to do as next step.

You have yet to hook up a scanner to monitoring the O2 sensors if I am correct. That's the first step. If you do not have one or are not willing to purchase one, then bring it to somebody who can. This should not be a hard fix. Best of luck.

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Wrong. I posted the scan codes after I scanned it. Porschtech3 pointed out I only posted codes for one bank (my bad) so I got the full set and re posted them.

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You mean you skimmed over The scanner points to both post O2 sensors, 2 weeks after they had already been replaced. Rich Fuel/Air mixture could be caused by bad O2 sensors since you can apply ground/plus voltage to the wiring returns to the DME to make it run rich or lean. I've reached the limits of what I can DIY. I'm down to taking it to the dealer to get it resolved once and for all. Our best Indy shop charged me 2k in an attempt to fix it, threw their hands up and said it would be too expensive and just drive it. I don't accept that premise. Not sure where the proof reading failed in the threads. I've written numerous professional articles, millions of emails over my career (no joke), in addition to proof reading books for varied publishers. This is the first comment I've ever had to that effect. If you can point to where I made the mistake, I'd appreciate it (In a DM) so I can learn to avoid the issue in the future. Nobody's perfect and I make no claims to be . My memory may be flagging in my ripe old age.

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Sorry if I missed it. I went back through the thread again and didn't see anything. Best of luck with the repair. If I were you, I would find a good independent to troubleshoot as the dealer is going to be extremely expensive and there is a good chance that they won't have a tech that is very familiar with a 996 as they are most likely working on cars still under warranty or just out of warranty. Please update us on this, we am interested in what you find. Sorry if I had a negative tone.

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Hi Paul, No need to be sorry. It's already been to the highest rated Indy shop in the area. Their conclusion was it would be too expensive to fix. My bad for not asking them what it was. Driving around with a CEL is irresponsible, so taking it to the dealer for an inspection and estimate is my next step. If it's simply reprogramming the DME, i will just let them handle it. Otherwise I hope the inspection will provide an answer I can DIY

I feel for you! But I think you are chasing issues without proper data. Before spending untold dollars on dealers, invest in a better diagnostics tool, many here swear by Durametric. If you plan to keep your Porsche for more than a couple of years, there will be payback. For example, rather than getting a maximum O2 sensor reading, with the Durametric you can see actual functioning of before/after voltages (and resistance, etc.). A Durametric allows you to see a wide variety of real time data besides your immediate problem (a good or bad thing, lol). I have a set of barely used MagnaFlow cats for sale in Marketplace if you are interested.

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Unfortunately the Duramatic software is not a viable option. I don't have the Windows OS on any of my PC's, never have and never will. You can thank Bill Gates for pissing me off in '91. However that's simply an aside and has no relevance to this conversation. I have every intention on keeping the car. It's been repainted from the bare metal up in the original color, and I just got it back after a complete rebuild suspension, all the bushings replaced, shocks and very, very unexpected and unwelcome rear axle replacement last week. All the the fluids were replaced and any service needed performed within 2 weeks of the purchase. The only documentation with it showed the engine replaced at 30k and the IMS bearing replaced. I have not done live any testing. As you point out my cheap Tandon may be incapable of showing anything I could find pertinent even if I could interpret the data. I've given the Indy shop a go when I first got it. It's my own fault I didn't ask what it would take to fix it after they said it would be too expensive and to simply drive it as is. That's on me. Otherwise I've not spent a dime blindly replacing parts. Now I'm going to the dealer for to have it inspected with an estimate that's only 10 min down the road and a complementary ride back home. The Indy is 45 min away in light traffic, 90 min if it's busy, and it doesn't have a complimentary ride back home. So I'll happily pay that Porsche tax willingly if they can pinpoint the issue and DIY if it isn't just a matter of reprogramming the DME. Failing that, I'll take it back to the Indy. I deeply appreciate the kindness, thoughts, insight and help the forum and this thread all the members have taken the time to contribute to. I'm humbled. Thank you for your input and time. I will keep the magnaflow cats in mind and DM you if that turns out to be the answer in the next 30 days. Doug

Quotes source post: 20631559

Thank you for the suggestion, time and interest, but I've already done both. It's been an interesting journey and time for me to bite the bullet and get it inspected by the dealer. As helpful and patient this forum and venue has been with me, it's time to go to the last resort I have that remains while kicking and screaming the entire way.. I don't trust a dealer further than I can spit, and I'm lucky if that simply doesn't dribble down my chin. I recognize I've hit the limits on my own DIY skill set, my resources and unwilling to spend another day hoping I'll find an answer. If the inspection turns up something I can do, I'll do that. I'll post the fix when it's been resolved. Thank you again.

This thread has been slow to technically get anywhere with 60+ post to finally get the 4 codes that are in question and are causing the CEL.. But "IF" the 02 heater circuit fuse is good and the wiring to the heater circuit is good, then the problem is the DME as I stated earlier... The DME pin #1 is the Controlling Ground Circuit that is responsible to heat up both post-cat 02 Sensors and control the Temperature so they will function quickly but will not overheat... Like I said previously, ECU Doctors can test and repair the DME... If you go to the Dealer they will want to replace the DME with a new one at $8000.00 + Labor .... How the Heated Oxygen Sensor Ground Circuit Controls Temperature via Resistance In a Heated Oxygen Sensor (HO2S) , the heater element is a small resistor embedded in the sensor body. This resistor is powered by a dedicated 12V circuit (often via a relay) and is designed to raise the sensor’s ceramic tip to about 600�F (315�C) so it can generate an accurate voltage signal almost immediately after engine start Engineer Fix . Role of the Ground Circuit The heater ground circuit is the return path for the current flowing through the heater element. Without a proper ground, the heater cannot draw current and will not heat the sensor. The Engine Control Module (ECM/PCM) controls this circuit by managing the ground side of the heater element Engineer Fix . Temperature Control via Resistance The heater element’s resistance is a key factor in how the ECM controls temperature: Resistance determines current draw : Ohm’s Law (I = V/R) means that for a fixed 12V supply, a lower resistance heater element draws more current, generating more heat. A higher resistance draws less current and produces less heat Engineer Fix . ECM adjusts duty cycle : Instead of simply turning the heater on/off, the ECM often uses Pulse Width Modulation (PWM) to control the average power delivered. By varying the “duty cycle” (percentage of time the heater is powered), the ECM can fine-tune the average current through the heater element Engineer Fix . Resistance changes with temperature : The heater element’s resistance is temperature-dependent. As it heats up, its resistance changes, which the ECM can monitor. This allows the system to adapt the PWM duty cycle in real time to maintain the target temperature Google Patents . Closed-loop feedback : Some advanced systems measure the heater’s resistance and map it to an estimated exhaust gas temperature. The ECM then adjusts the heater control signal to keep the sensor at the optimal operating point Google Patents . Why This Matters By controlling the ground circuit and the current through the heater’s resistance, the ECM can: Heat the sensor quickly for faster closed-loop operation. Maintain a stable operating temperature for accurate oxygen readings. Adapt to varying engine conditions (cold start, hot idle, load changes). In short: The heater ground circuit’s current is controlled by the ECM’s PWM duty cycle, which is adjusted based on the heater’s resistance and temperature feedback, allowing precise control of the sensor’s temperature

Quotes source post: 20569567

I love these threads that go on forever and the OP never really does what�s necessary to �troubleshoot� the problem (ie: in a linear, if-then fashion).

If it's running that rich do you have to worry about bore score from fuel washing the cylinder walls? What are your fuel trims ?

Quotes source post: 20631906

60 posts are wee bit exaggerated, you were already getting fed up by first 20 or so when I originally didn't post all the codes and I realized my rookie mistake. OBDC didn't exist when I was a mechanic. So it was my first time use of a scanner. But you're correct, this thread has long since not produced much more than noise after the first couple pages. If I hadn't attempted to answer every post it would have been far less. It's a holdover from my customer service days to never just quite responding. I need to minimize my soliloquies that are the result of at least half of the noise. The O2 sensors are good . (Some idiot initially tested the wrong wires from the DME to the heaters and didn't get the expected 12v), I plan on taking it into the dealer mid-next week and wait to have it inspected. I certainly don't expect you to teach me to be mechanic. It's best I learn on my own. I can use a wrench and read schematics. If it's only a DME issue, I'll have them fix it as long if it's a simple reprogramming issue. Otherwise I plan on sending out to the people you recommended by 3 or so pages into the thread and your recent post.

I wasn't exaggerating at all !!....... It was exactly 61 posts before we got all 4 codes that are in question... We do get a lot of Threads that are not Technical in nature, but since this is a Technical Forum it is expected to be Technical when applicable, so I you don't want Technical help then please indicate it at the beginning of the Thread.. I will politely shut up now..... it is your Thread ....

Quotes source post: 20634501

I bow to your attention to detail. It is I that needs to politely shut my trap until I actually have an answer to the question plaguing me. 5 more days until the dealer inspection appointment. I hope to get to the bottom of this without causing further disruption your day. You help has been deeply appreciated.

Quotes source post: 20642900

It's not disrupting my day, troubleshooting ICE problems is something I have done for 50 years and I have to do it to stay happy.....lol An old saying is to keep from being depressed you must use ALL your skillz ........So I troubleshoot sh*t , and I fix sh*t .....

Hi, I used ECU DOCTOR for this issue. When i got everything back they had program my car for automatic instead of manual and since i have an ABS/PSM light on all the time. Trying to fix it but Piwis won't allow me to change it

Final Answer: From the dealer. it's the DME. Off to be repaired/rebuilt now.