Bad cat, no codes, have durametric, need HELP!

First, let me make it clear I'm pretty much a computer idiot. I'm desperate to get through California smog. My car is a 2004 996 40th (with X51) I get no check lights, codes or codes pending and the car runs great however I failed smog. My OBD2 indicates a red check at the catalyst, everything else indicates ready. I took the car to my wiz mechanic for analysis and his young minion tells me I have a bad catalytic converter on bank 1 but that he will not replace it with anything other than a new factory part$$$. This analysis supposedly took a couple of hours to determine, which actually makes me suspicious of the analysis. I'm pretty sure they have the PS1 or whatever it's called factory service computer. I took the car home and assumed there diagnosis was correct, I replaced the bank 1 cat myself with a supposedly good used one but I am not getting any love. I've done many miles of driving in various mech advised conditions. I'm getting the same result that I got with my original supposedly bad cat which I also drove for many miles trying to get it to light off. Something in me suspects the mechanics analysis. On the other hand, possibly I have purchased a second bad cat. My question is when I plug in my Durametric, what exactly should I be looking for to determine whether I do indeed have a bad cat or maybe a bad downstream O2 sensor? I've got to get through smog and I don't want to spend the money on a cat unless I know that the problem will be solved. Thanks in advance, Paul

Possibly not much help, but if you had/have a bad cat it will throw codes related to the O2 sensors. When you say "Duratech" is that actually Durametric? If it is Durametric then you can read the O2 voltage levels pre and post cats. Might make sense to clear everything by taking the negative lead off the battery. That will reset the DME back to a default map. Then you will have to drive through various cycles to have the DME readiness cycle complete.

Read this post hopfully will help you out . https://rennlist.com/forums/996-foru...33-smog-3.html

Yes Durametric sorry, worse yet, the box happens to be 2" from the keyboard. And now I see the voltage levels I should be looking for thanks to Kuwaiti. Car uses very little oil and I only run Chevron or Shell Super so no reason to think the cats are clogged. I did disconnect the battery for an hour last week with no change. I'm going to try the drive cycle tomorrow morning. Actually the drive cycle thing makes more sense than anything else. I literally never drive in that low 3000 rpm with the X51 package, its always 4000 rpm minimum. Also the real clue I think is the fact that there are no codes or pending codes, so the computers are not seeing any problems. Will post results Monday

This worked for me. Driving tips AFTER DME reset: - Start car and idle for 2 min (SAI pump should be ON and then OFF) - Start driving the car but try to keep the rev below 3k at all times. Just drive 10-15 min local roads, then 10-20 min freeway. The trick is NOT to go over 3k if possible because most tests require rpm < $3k (or engine idle) to perform. Also, on freeway try to maintain as constant speed as possible (rpm < 3k). - Park the car but leave the engine idling for 5 min or so - Now all your readiness flags should set (maybe except the cats). The cat readiness may need the same driving on the NEXT day to set if the cats are healthy.

You need to find a shop with a Porsche computer. They can force the cat readiness to be "ready." This is what they do after a repair because Porsche dealers cannot have their mechanic drive customer cars for hours on the freeway to complete a drive cycle. I had this once, and a shop just forced the computer to be ready.

bad news Still have "CAT-NOT READY" indicator after several drive attempts. No codes thrown and non stored and never have been. Observed all drive cycle requirements several times. This was pretty humiliating being the old Silverback driving the silver Porsche in the slow lane. People around here are driving hugely fast on the freeways on the weekends due to lack of traffic. At one point I was actually scolded by an old lady in her Cadillac. I talked to Dwayne at Vision Motorsports, the very well known repair shop that did the original analysis and we are going to double check everything related to potential cat problems on Wednesday. He says he has never had to change so many cats as on the 2000-2010 911's and Boxter's. On Porsches older than 2000 the cats last forever. I would imagine it is related to a cheapening of the precious coating. I don't believe he can force "Emissions Ready", though he does have the Porsche work computer. I will post results on Wed.

I'm not sure if you can leave the durametric plugged in while driving. But I plugged this in and was able to see the readiness status on my phone in real time. Good luck. I did normal driving for 800 miles with no luck. One attempt with what I posted above cleared everything. https://www.amazon.com/gp/product/B00T5G53ZM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 https://www.amazon.com/gp/product/B00T5G53ZM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

You can plug in the Durametric while you drive. I didn't do it because I didn't want the distraction. I tried that drive cycle exactly, in fact I tried it 3 times with no luck.

Not much help. Just a data point. My 04 C4S has an aftermarket X Pipe that i recently installed due to the cats failing. Literally coming apart. I track my car though. Anyways..... my cats dont meet the requirement and will set a engine light. Being a tech i have an onboard dongle in my car so i can reset and check codes instantly. Im too lazy to install my extenders to "fix" the issue right now. But my OCD wont let me leave the light on. I must clear it the moment it turns on. Again, anyways....... drive cycles are a huge pain to reset. Sometimes it can be done in less than 50 miles and the codes back. Other times it can take 300+ miles. It dosent surprise me that your having a hard time. In the shop we see it a lot. We dont have emissions testing in florida so we dont have to care though. Just keep tacking the miles on it and it will complete the cycle eventually. Also. This may have been discussed in this thread and i didnt notice it. But to confirm you cats are working is easy if you have a scan tool. All you need to do is be able to graph the O2 sensors and watch the waveform. Once the cats are up to temp all you need to do is compare the upstream O2 to the downstream O2 sensors activity. The upstream will have a lot of activity. You will see consistant movement of the graph. The downstream should have very little activity and some times almost none. Obviously there is a mathmatical calculations that the computer is looking at. But the general rule of thumb i have seen is the downstream should have less than 1/3 of the activity of the upstream. Again this must only be looked at when they are up to operating temps. Assuming your cats are good you could easily see the difference by watching them on a cold start. On a cold start the upstream and downstream reading will virtually mimmic each other as the cats dont work cold. As the Cat warms up (a good one at least) the downstream activity will slowdown. Hope that makes sense and helps.

Small bit of additional data points. Codes are very specific in this case to identify the issue. What was the codes stored im the begining that made the call is a bad cat? Bad cat codes are either P0420 or P0430. These 2 codes are almost always a bad cat. Any other code store is almost never a bad cat. Her is a pic of the wave forms of a bad cat (google images - not porsche specific). Note the upstream and down have almost the same activity. Now here is a pic of perfect cats. Note the downstream is flatlined. Also to note. Watch these waveforms at idle or near idle while in park or neutral. Also a point. some drive cycles also require the car to be started from a cold start (intake temp, coolant temp amd ambient all match). Then car drive through many situations. Then left to get cold again. Then this cycle repeat several times before its actually considered a drive cycle.

Actually you have made it very clear what I should be looking for regarding O2 sensors vs bad cats. When I checked the O2 sensors with the Durametric last week they appeared to be working as you described. As I said, there have never been any codes stored or active at any time in the last few years. Each drive cycle was performed from cold start. Other than the "CAT" red X mark on the OBD2 Emissions Test Ready monitor, all other emissions systems have a green check mark throughout this whole process. I am going back to the mech today to recheck before spending for the replacement cats. Still its a mystery how you can have such a major smog issue such as a bad catalytic converter and yet not have any red lights on the dash or throw any codes or even pending codes. It just doesn't make sense. If the cat proves to be bad I am tempted to get the Magnaflo CARB legal replacements. 2500$ for one Porsche factory driver side cat is over the top.

I can't speak on emission testing equipment as i am a tech in a state that doesn't do actual tail pipe testing. However, if you have never had a code stored (P0420 or P430 Catalytic Effeciency below threshold) and at some point the readiness monitor was done, then the cats are in perfect working order. You may want to see a different mechanic/testing facility. Perhaps the person who did the test is not experienced and assumed the readiness monitor was indicating the cat was bad. Some others have commented about forcing the readiness monitor. I can't speak on that either although i can say i do have aftermarket and factory scan tools (not for porsche) and have never seen and function that has given us that ability. I can only attest that the specific conditions for the monitor to go green are very very specific. Some of the include things like getting up to 60 mph and the coasting back to 20 mph without braking. Its insane what has to be done in some instances. The term "drive cycle" is a bad term in my eyes. It makes people assume they can easily go drive the car in a certain set of conditions and it will pass the readiness monitor. In truth the PCM looks at a lot of data over a certain time frame and watches for thoses particular conditions. You may meet some of those on 1 test drive and not meet the others until your 13th test drive. Here is a basic explanation from one of the classes i have been too. Its basic but explains how detailed it is. How to Perform a Basic Drive Cycle Here are step-by-step instructions on how to perform a basic, yet very effective, drive cycle that will complete the readiness monitors for your vehicle's emissions control system. Step One: How to Prepare Your Vehicle Have the fuel tank between 30 and 70 percent full. Some systems, especially the EVAP system, need to have a specific level of fuel in order for the tests to be trusted. If the fuel tank is near empty or completely full, many of the basic tests will not run at all. The vehicle must also have a good alternator and a strong battery. If you have to occasionally jump-start your vehicle, all of the memory from the powertrain control module (PCM) is erased, which includes the data that accurately tracks the results from various stages of the Drive Cycle. Also, if the battery is weak or undercharged, some of the most important tests will never run. The vehicle must sit overnight, or for at least eight hours, in an environment that is less than 90� F. The engine temperature needs to match the air temperature in order to establish an accurate baseline for the testing. If the outside temperature is over 90� F, the fuel is too volatile and the EVAP system won't even try to run its tests, though some of the other emissions systems may run their tests. The keys must be out of the ignition and all of the doors must be closed while the vehicle sits over night because many of the onboard computers "boot up" when the keys are in the ignition. Also, many of the onboard computers still run until all of the doors are closed after the vehicle is shut off and the keys are removed. Step Two: The Cold Start Start the vehicle and let it idle for two to three minutes in Park or Neutral. While it is idling, turn on the head lights, heater/defroster, and rear defroster for a three to five minute warm-up phase. Let the idle speed settle down to near the normal speed. Next, put the vehicle in gear and drive through city streets at about 25 mph. Go up to about 35 to 40 mph a few times before slowing down to stop. Don't roll through the stop; be sure the car is really stopped, just like you learned in driving school. Accelerate from each stop in a normal fashion—not overly conservative, but not like you are competing in a drag race either. Step Three: A Short Freeway Trip After the vehicle has been cold started and driven for a few miles on city streets, the next step is to take it on a short freeway trip. Enter the freeway on-ramp and allow enough room with respect to other vehicles so that you can do a 1/2 to 3/4 throttle acceleration up to freeway speed. When you have accelerated up to around 60 mph and have safely merged into the flow of traffic, stay in the slow lane and maintain a steady speed of 55 to 60 mph for a minimum of five miles. Please use the cruise control to help you maintain speed. Find a nice, long off ramp to exit from the freeway. As you exit, take your foot off of the accelerator and let the vehicle coast down until it stops under its own power as you complete your exit from the freeway. Do not use the foot brake and do not shift gears until the very end of this "coast down" phase. Step Four: More City Driving After you have completed the freeway trip, drive through the city streets for a repeat of the second part of Step Two. Go up to about 35 to 40 mph a few times and then maintain a city speed of 25 mph before slowing down to stop. Again, don't roll through the stop and make sure to accelerate normally. Pull in to a parking place and let the engine idle for one to two minutes and then shut it off. Step Five: Have your Readiness Monitors Checked and Verified Drive your vehicle to your regular shop and have them re-check your readiness monitors, present codes, and pending codes. They should do this as a courtesy and for free. If all of your monitors are "ready" and there are no present or pending codes, then your vehicle has been properly repaired and is ready for an emissions inspection and for normal driving.

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Move to Florida. No state taxes and no nanny emissions testing or requirements. Problem solved.

Just a thought do to our ( mine anyway ) speedometer not reading true speed do the drive cycle with couple of mph above the speed or under the speed suggested .

Much delayed follow-up, I did finally pass CA smog. Remember it was only my CAT REDINESS that would not set. There were and never have been any check lights on the dash and there were no codes nor pending codes. Here's what I did; First I replaced the downstream O2 sensors. went on several drives and NO luck. Second, I replaced the MAF sensor. Went on several drives and NO luck. Decided to pony up for new cats. I bought the CARB legal Magnaflow cats on Amazon for $650 each plus $60 shipping. There was no way I was going to spend $5000 for factory cats for a $30k car. The Magnaflow cats are really crappy, like third world quality. They look nothing like the photos on there web site. The cat elements are much smaller than the factory cats (maybe 1/3 the element volume) and the housing is a very thin single wall can. There is no way they are going to last as long as the original factory parts. They fit like crap and have hard contact at the crossover area. A plus is that they are very light compared to the original. THE IMPORTANT PART IS THAT THEY DO WORK. I started the car cold and let warm up for 5 minutes, got in and drove to the freeway at less than 3000 RPM in the various gears, got on the freeway and put it in 6th gear which was about 2300RPM. at that point I turned on the cruise control and rode it out in the slow lane. Ten minutes later almost to the second my plugged in OBD2 reader showed a green check in the CAT REDINESS section YAY!!! The slow down without touching the brakes is total BS. You don't need to do this and obviously it is very dangerous to do on the freeway so it makes sense that it is not required . I went for coffee and checked the OBD@ on restart and all was still good as it is today after 2 weeks of normal and high speed 100+ driving. What I learned through research; The CAT READY is the last function to set only after all other emissions checks have completed and show green . The only exemption to this is the EVAP system. Also learned reading CARB catalytic converter mandate, If your cat is more than 2.5% inefficient it will not set the OBD2 Emissions Readiness, Though the car itself is perfectly happy hence no check lights on the dash. I am an old ex F! fabricator so I had to see what was inside the Porsche cats. I cut one apart and am amazed at how well made it is. At some points there are 3 different layers of tight slip fit but not welded stainless steel all sculpted to guide the exhaust flow. The external welds are excellent robotic MIG welds. The cat membranes or cans as they are called are huge 120mm Dia. x 100mm and 102mm Dia x 100mm long and of the best quality. The Porsche cats are among the most expensive cats you can buy for any production vehicle. Ferrari cats for the same year are a1/3 the price of the Porsche parts. Thanks to All for your help and I hope this post will help others. Paul VDL

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And there is a reason why professional mechanic insists on installing only factory cats. They work, they are high quality, and they don't have time to try everything on earth. By the way, your mechanic did say that you had a bad cat so � his diagnosis was correct. There is no way Porsche cats are more expensive than a 2004 Ferrari 430 cats or 360 cats. Those are $13,000 a set.

yelcab, You are correct, the mechanic initially advised new cats. What I didn't mention in all the above is that I returned to the mechanic and we further analyzed the car sitting side by side while the poor car idled for 70 minutes in his shop plugged into the special factory $20K computer. The "advise" he gave based on that input was to first change the O2's and if that didn't work, change the MAF and if that didn't work change the Cats as a last resort. The point is, using the factory shop tool, all appeared to be within spec (timing, O2 sensors, coils, ignition, fuel, temps, etc, etc....) Personally I'm going to put the old factory Cats back on and save the Magnaflows for the smog testing only. Not to get into a pissing match but doing a more thorough F360 search I did find the new Ferrari factory cats for a price just a little less than the 996.

There's a used set in the marketplace right now.

Only thing is, you wont know if there good until you've put in the effort to install them and take the car for a slow <60mph drive. New ones on Amazon for $650 each. BTW, I have always loved your Flintstones avatar. Where did you find that?