Fault code P0430

Hi guys, Im trying to figure out a code P0430 I get about once per month since I took the car out of storage. The car had a full tank of gas treated with Sta-Bil and was stored for about 6 months. The MAF sensor was cleaned during summer 18' and a new air filter was installed. When I took the car out of storage I got the first P0430 code. I said to myself it was probably the Sta-Bil treatment going through the system with the old gas acting up on the readings. Cleared the code. I got thought the full tank of gas, refueled with 94 octane and did the bi-annual oil change. I did topping off the oil, middle of the gage and the car havent burn oil since then. Today I got another P0430 and I decided to analyse the STFT and LTFT especially on Bank 2. The first time I got the code on May 10 the values were the following: STFT Bank 1: 6.3% LTFT Bank 1: 2.3% STFT Bank 2: 6.3% LTFT Bank 2: 1.6% RPM: 2200rpms So if I do the maths: Difference in % Bank 1: 4% Bank 2: 4.7% ------------------------- 0.7% difference = acceptable Difference in actual number for LTFT LTFT Bank 1 0.977 LTFT Bank 2 0.984 So everything seems very good from the STFT and LTFT and within acceptable limits of 10% difference and based on the acceptable part-load range of 0.7 to 1.32 (where 1 is considered no trims) The second time I got the code P0430 June 5th the values were the following: STFT Bank 1: -4.7% LTFT Bank 1: 7.0% STFT Bank 2: -7.0% LTFT Bank 2: 4.7% RPMs: 2360 If I do the maths: Difference in % Bank 1: 2.3% Bank 2: -2.3% -------------------------- 4% difference = acceptable Difference in actual number for LTFT LTFT Bank 1 0.930 LTFT Bank 2 0.953 Again everything seems good from the STFT and LTFT except Bank 1 and Bank 2 have a difference lean/rich but within acceptable limits of 10% difference and based on the acceptable part-load range of 0.7 to 1.32. I also experience what I can call rough idle after getting off the highway at a stop light. The car have 149000kms 4 oxygen sensors were changed at 117000kms Both catalyst converter were changed at 125032kms Spark plugs were changed at 131575kms and will be redone soon. I plan on cleaning the secondary air injection pump as I also get a P0491 code once in awhile. I dont own a Durametric for the moment but I plan buying one so I dont have 02 voltage for the moment. Anyway I would like to find what cause the cell. As I dont see anything wrong with STFT and LTFT readings can you point out what I should try first? I was really expecting weird readings from the fuel trims if an 02 or catalyst converter were faulty. Is there something I dont understand? Thanks Hugo

Cleaning your MAF is not a reliable treatment. Only when it is dirty it might restore (temporarily) its functionality after cleaning, If it is old it makes sense to replace it. Did you check the MAF sensor hot film voltage? With ignition on, engine off: It should read around 1.0V Porsche service manual indicates 0.9-1.1V as a okay range Maybe it has nothing to do with your actual problem but m y personal experience is that a more then 0.05 V offset is already detrimental for performance. The car will run fine without fault codes but will not pull as strong as compared to a new one.

Your looking at this from the wrong direction. The code P0430 "Catalyst System Efficiency Below Threshold Bank 2" has nothing to do with your fuel trims. The code is indicating that your Catalytic Converter for Bank 2 is no longer doing its job. The PCM monitors the Upstream O2 and Downstream O2 and compares the 2 against each other. In simple terms it monitors how often the signal switches from rich to lean once fully warmed up. To keep it really simple it is more or less like the upstream is watching what goes in to the CAT and the downstream is watching what comes out. They should never be the same (except during cold starts). When the PCM see's that the signals are the same or close to the same it understands that the CAT is no longer performing its emissions duties and is telling you so. Considering the age of most 996's it is no surprise to see this issue. Now if you had Lean codes, Rich codes, O2 sensor codes or misfires i would suggest correcting those issues first as they could cause false reading. The reason it takes a while for the code to return is the PCM needs to see a lot of data before it will make that decision (it's called a readiness monitor). Simply put.......You need a new Catalytic Converter for Bank 2 and it wouldn't surprise me if Bank 1 was quick to follow. It is possible that the Converter that were installed do not meet the specs the PCM is looking for. What brand were they? Warranty?

From a book I have

Topic starter writes that o2 sensors and cat converter were recently changed Do you have a stock exhaust?

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^This

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Hi guys, Thanks for your replies! I will try to add as much details as I can here. No I havent check the voltage but I will try to find the correct pins and test it. The MAF sensor is also brand new and was changed by a Bosch unit, not from Porsche at 135000kms. A new throttle body was also fitted at the same time. Alright, I was under the impression that fuel trims would be out of range if the 02 sensors were bad. But I understand now how this thinking was wrong. Its in fact because the 02 are working correctly that I get this code. I also dont have any other codes related with 02 sensors or misfires. It is a possibility that the actual CAT installed doesnt meet the PCM requirements. The past owner changed them. I took a picture of the cats and I can read a reference number that doesnt tell me much.. You can read the reference code on the driver side CAT Thanks Paul! I will study this and try to test what the document is pointing out ASAP. Yes and no... I had a factory sport exhaust that was retro fitted. No more information about this except that they did everything and even installed a switch for opening and closing the baffles but I know it was not a stock option and was retro fitted.

That picture looks like aftermarket "universal" weld in converters. I have installed hundreds of Cats, both factory OE parts and aftermarket. What i have found is the OE always works perfect (duh, but who can afford them), the "direct fit" converters made by name brand exhaust companies almost always fit perfect and meet the happy requirements of the PCM. sadly i have seen WAY too many times where the exhaust shop special weld in one size fits all converters don't last and don't work right out of the box. My suggestion would be to get the car (and CAT) up to operating temps and watch the upstream and downstream O2's. Compare them to each other watching the info as a graph. Start the car cold so you can see the how they will look if the cat is 100% shot. Picture this. When cold, or when the cat is shot, the front and rear O2's will be virtually identical graph's . When the CAT is hot and working normal the upstream should be switching constantly and the downstream should have little to no activity, maybe 1/3 of the upstreams activity if that. If you notice that once the CAT is hot the activity is close to the same you have confirmed a bad cat. Then becomes the question of what killed it? Is it just a cheap part that doesn't meet criteria? Did someone drive for a prolonged time with a misfire and the unburnt fuel damage it? Is coolant leaking internal in the engine and being consumed in the combustion chamber? Again, since you stated the fuel trims are within specs i wouldn't think its caused by the engine. I would suspect a cheap cat.....

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Perfect thanks! I would defenately need a Durametric one day... Funny as it is I was about to buy one but I guess the money will go on new CAT. I made a quick test and hammered both CAT on the car. Bank 1 is making a very bad metallic noise when it hit it while bank 2 doesnt make much sound. Funny that bank 2 seems to be the problem. I found on bank 2 side a small exhaust leak... I dont know yet if the joints are the problem or the little crack in the middle I will have to verify this ASAP. I guess I can always tight the collars if there is a problem Changing the CATs is defenately on the list... My original plan was to change the injectors as a preventive maintenance but I guess CAT are more important for now. Do you think I should re-use my actual 02 sensors or replace them? As for the CAT I will defenatly go with aftermarket ones.. I just can't justify OE price.. Any suggestion about what to use (Still have to do some research about 200 cell cats) I also found Pacesetter cats which are priced really low... anyone have exprience with theses? Here a link from RockAuto: https://www.rockauto.com/fr/catalog/...converter,5808 Thanks Hugo

The minor leaks at the joints are not much of a concern. If it is something you can hear then yes, clean the leak up some how. Some leaks are actually by design to allow moisture/water to exit the system. As long as the O2 sensors are switching they should be o.k. I have heard of the Bosal brand on rock auto... they are good.....not sure about the others.... Also to note. The code only means it is no longer emissions compliant. That dosent mean it is going to effect the car in any other way. I live in florida where we dont have emissions testing. Most customer opt not to repair them and just deal with the light ( My OCD won't allow a check engine light on). On the other hand if the CAT is coming apart it can and eventually will cause a blockage in the exhaust which then will cause drivability issues. Now you can decide whats more important.....no compliant cats or new injectors...

I can recommend the TopGear 200cell cross over cats very good build quality and perfect fit. running already 35.000km with them without a problem.

I would buy a used OEM cat.....they can be found in the "downpipe" section of ebay: https://www.ebay.com/sch/i.html?_fro...npipe&_sacat=0 I have never seen an aftermarket cat that works correctly or lasts more than a year. I'm not saying they don't exist, but the OEM cats are far superior.

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Thanks for the direct link Paul! You think it could worth the money and effort to buy used cats? I can't believe the previous owner let the shop throw the OEM ones in the trash........... Something I should know before buying, something I can ask to the seller.. milage on the units, usage or it doesnt even matter and its a matter of luck? On a side note I was just about to ask a question about FVD Bromacher cats... I was looking at their 100 cell but I guess I will need to clear codes all the time. Anybody use 100 cell cats without issues? The reason why I was looking at 100 cell instead of 200 cell is the price difference.... They have a set of 100 Cell for PSE exhaust at 1200$us which make it interresting compared to 1700$us for the 200cell PSE. I also would like to know the difference between ''Normal'' CAT and for PSE exhaust? I wasnt aware that there could be a fitment issue so what is the difference is there's any? I want to change my actual cats not because of the code it throw once per month but because Im affraid they become blocked and damage the engine. I also dont have to pass emission tests where I live. I plan on tracking the car a couple times per year with PCA, the car is not my daily driver and is used to have fun in the mountains but It also see some street use with my son and wife in the car. Here the link to the model im refering to: 100Cell: https://www.fvd.net/us-en/21011118K/...e-exhaust.html 200Cell: https://www.fvd.net/us-en/21011122K/...e-exhaust.html Before I forgot I also found Schnell performance Sport Cat that are decently priced. Never heard of them before so I defenately have to gather more infos but I wonder how they perform. https://schnellperformance.com/produ...nverter-x-pipe Thanks again for you help, couldnt be more satisfied to be a member of this forum! Hugo

100cell will certainly not be without CEL You would need a ecu tune to cope with that and also with the different back pressure

I've had good luck with 200 cell cats. Good performance, no warning lights or codes, pass annual emissions testing (required here). I've run them (two different sets, but both 200 cell cats) on a 3.4 and a 3.6, with stock ecu tunes.

Just another idea for you to think about... Since you don't need to pass emission test in your area, you could always get rid of the cats. Either get a cat bypass pipe or remove the current pipes and just knock/gut them out. To remedy the check engine light you can either use something like Fabspeed sells or go on ebay and get something cheap. If you have the clearence at the O2 sensors. This setup just tricks the pcm into thinking the Cat is there and is running perfect. https://www.fabspeed.com/universal-9...nverters-pair/

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Thanks again for helping me out! very good idea! As you can see Im not really used to deal with exhaust parts... first time I have to play with exhaust on a 4 cycles engine. I will still gather informations about cat bypass as I dont want to lose much low / mid torque but that is an interresting solution. As I dont plan to reprogram the DME I would like to have a confirmation that using bypass wont cause any problem with the engine. Im basicly sure the engine are restricted alot with cats installed and its mapped accordingly. I also have another solution which is Carnewal 200 cell... I contacted then and they cat sell me OEM cats that has been modified with 200 cells. Im waiting for a price quote and I will ake my decision after I got it. So far I think the cats delete will the cheapest solution and as long as it dont cause any problem with the engine it is really interresting!

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Hi! Just a little follow-up. I decided to get rid if the cats as you suggested. Difference between both setup 200cell vs cat bypass was 1000$.. As I dont want to take the chance of burning another set of cats Im better get rid of them. Here's what I will use to space the 02 sensor: http://www.bigdaddiesgarage.com/mini-cat-cel-fix.html I will post some pictures of the installation. I decided to go with FVD X-desing bypass.

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Glad to hear.... please keep us updated. I have been on the fence about getting rid of my cats but i have heard it kills low end torque. Would love to hear another opinion.....also curious on the exhaust note.. i have a fabspeed competition intake and maxflow mufflers. It sounds good but just not enough. I wish i did supercup muffler but heard too many people complain about a drone at highway speeds. Maybe an X pipe would be the extra i need.

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Ok..... After my order has been cancelled because he X-pipe is out of stock I went with Carnewal 200Cell... I was my second choice price wise and I have heard good things about the 200cell option. There is also a couple more reasons why its a good "bad luck" for me... 1st: The cats he use are OEM.. as Im keeping the car stock and kind of "restoring'' it I prefer have the stock cats look. 2nd: My car is on the street 90% of its life time so my 2500 to 4000rpm range is important. The downside is I was expecting a more "rev happy" engine with the Xpipe. My understanding was to keep back pressure by keeping the stock mufflers, take off some back pressure getting rid of the cats and enjoy. As a winter project I will empty my actual cats so I will be able to test both setup.

Just a quick follow-up. I installed the Carnewal 200 cells cats today. The installation was easy and took me 1h30. Not a major change in sound but you can hear a richer and deeper sound than before. I really like it! And so far the code hasnt returned.

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pour Dura lube in your tank, buy it at walmart,problem solved