Exhaust codes

Seems like I have lost 20HP and cant find a reason for it!!! Ever since I installed catless header and catback with EVO software I got a cel with readings P0421 and P0431. Since the car seemed to be running fine and made good HP increase I left the issue alone. Now, I recently changed my cheap header for a SuperSprint and gained two more codes ( P2196 and P0159). Took the car for a Mustang Dyno ride to find out that I lost 20HP. AFR was considerably leaner and the lost HP was even accross the band. I found a couple of previous old posts on this codes to find that SuperSprint header has caused this to other members before and it is not a definite issue related to faulty O2 sensors and the only fix I saw claimed to be performed on the P2196 which was to install spacers between the O2 sensors and header. Well I had already done that with the 421 and 431 the first time those showed up. Looking the P2196 it says the sensor stuck on rich and may need to replace sensor and the P0159 says there is a fault symptom : "open circuit behind "cat" on bank 2. Thoughts? Thanks Jose

Yes I don't understand why the EVO software wouldn't take care of your O2 sensors so they don't trip a 421 and 431 code. Those codes are for pre-cat warmup cycle and occur when the reading the first and second O2 sensors send to the ECU are outside the acceptable range. When you have catless headers you will ALWAYS get these codes unless you have ECU tuning that basically shuts off the second O2 sensor and fools the ECU into always thnking the O2 readings are fine when using headers . I would contact EVO and see if that is a feature of their ECU software or not. If not, then I'd suggest getting an ECU flash that does take care of that issue. If EVO says theirs fixes that, then have them reflash your car or find out why it isn't working in your case. As for headers , different headers produce different results and YES there have been several instances of where catless headers actually LOSE power vs. ones with cats. I suspect it has to do with exhaust backpressure and exhaust tuning.

K-Man S In regards to 421 & 431 I already had comunication with Zuccone and Ian and neither were able to help. They just say they dont understand the codes. I stopped insisting for assitance because the car was running great at the time and I was just looking for a way to erase the code to stop that amber light which blinds me everytime it comes up. (As I keep erasing it with my Durametric). In regards to the header I have always had a catless one "made in China" since the begining before I sent my my ECU to the EVO facilities for a flash and I even told them that the car would be fully catless. The other codes I am concerned now are the P2196 and the P0159 which are the only readings I am getting when I found out about the HP loss. In the other hand I can understand that different headers might show differences in a few + or - but not as much as -20hp. Next week I will install my "made in china" back and see what happens. Thanks Jose

Dyno run attached

I'm surprised EVO doesn't understand basic O2 sensor operations and the codes that come from them if you run open headers . You need different ECU programming IMHO to at least get rid of the 421/431 codes. As for the other 2 codes you might ask Scott at Softronic to look them up since he is also the PCA Cayman tech person and has access to all of the codes. Speaking of codes, here are the results for the other 2: P0159 Oxygen sensor behind catalytic converter , dynamism NOTE The catalytic converter is filled with oxygen during the thrust phase, the oxygen sensor behind the catalytic converter should recognize a lean mixture. If this is not carried out in an appropriate amount of time, the oxygen sensor is determined to be inert. Diagnostic conditions Thrust phase for a minimum of 5 seconds Oxygen sensors behind catalytic converter ready for operation Basic adaptation stabilized No other oxygen-sensor faults Possible fault causes Oxygen sensor faulty (dynamically inert) P2196 Lambda correction downstream, bank 1 – rich/lean control limit exceeded NOTE Diagnosis detects a deviation between the lambda value measured by the oxygen sensor upstream and the value measured by the oxygen sensor downstream. The deviation is eliminated through adaptation, a fault is only set once the adaptation limits are exceeded. Oxygen sensing upstream active No fault for secondary air injection, catalytic converter or tank vent entered Possible fault causes The most common fault cause is a leakage between the two oxygen sensors, resulting in the sensor downstream measuring more residual oxygen in the exhaust than the sensor upstream. Diagnostic conditions Engine running No faults detected for oxygen sensor or oxygen sensor heater up and downstream Leakage in exhaust system between the two oxygen sensors Oxygen sensor upstream faulty (contaminated/aged) Sounds like you have one or more faulty O2 sensors, if it is your upstream sensor then that WILL have a big impact on your performance because your ECU won't exceed certain limits without proper values from the sensors. That or you have a leak between the two sensors somehow, but I think you'd hear/see that and you haven't reported anything like that. Just my 2 cents but I think you need open header appropriate ECU tuning that will take care of your O2 readings, although at this point you may have one or more bad O2 sensors which need to be replaced as well.

K-Man S Greatly appreciate your assitance. I believe I now have a better idea on how to approach this. I have emailed EVo asking about the second O2 sensor effect from their software and I am waiting for the response even though I have placed an order for 2 new ones. In regards to Campioni I am also waiting for their response on the P2196 since I have also discovered that other Cayman owners have faced the same problem as well as BMW owners with SS header. The only fix mentioned has been the addition of straight O2 18 mm simulator which I already have. I suspect that part of this problem with SS headers comes from the 2 bongs almost facing each other. Also, during the weekend i found a site with "the cure" for Cayman 's with P0420's and P0430's with the use of a 90 degree O2 sensor simulator. Those have been ordered as well. In theory I might have the solution for my P0421, P0431 and P0159. If after fixing the 3 mentioned codes the P2196 still comes up I will install my old header back. Thanks again Jose

Hi Jose, I've been following this thread and I also have the P0431 code but with the stock exhaust (no mods on my 06 CS). Can you please post where you were able to find "the cure"? My CEL comes up with that code intermittently. Any link, if allowed, would be greatly appreciated. Thank you.

Shiftercartracer; In my case getting the P0421 & 431 on a catless car is normal. The O2 simulator I am mentioning works for this purpose. In your case if you have a P0431 it is likely because you have a real problem with a catalytic converter or even an O2 sensor . Get your car to a shop to have it properly diagnosed. I believe your 431 is on the passenger side and I would just have the shop starting by taking a look at the cats on that side. Best wishes, Jose

I ended up replacing all 4 sensors and P2196 is gone. My AFR came back to normal but did not gained all my hp back. Later installed my old catless header back and the car did much better. I also learned that my EVO software was not what I requested for or needed as it was not programmed for a catless car. (this explains the P0421 and P0431) I am in comunication with Evolution Motorsports to re tune my ECU after I fix my issue with P0159. Kind of facing a dead end here because I have already replaced all sensors and the description for P0159 is a faulty sensor on bank 2 specifically. I have erased this code 3 times after replacing the O2 sensors and even though it takes longer to come back it eventually shows up again. My Durametric describes a P0159 and a more sophisticated equipment shows the same fault as pending. As a side note; the simulators did worked also and the P0421 & P0431 did not showed up again. Jose

K-Man S I think it has to do with the ECU flash. My car has an RS370 kit installed and a few other mods. For this reason my local shop wont even change my oil. I can only think that the proper re tune should fix this. As always, greatly appreciate your asistance! Jose

Thank you very much K-man. I will contact my dealer. I've also read the same thing somewhere that the emissions issues "should" be covered.