Hi I am trying to do some diagnosis on my car: I keep getting a CEL for Bank 1, post cat O2 sensor stuck on lean error code. When I plug in the xdiag pro 3 reader for ferrari, trying to see what I can read, it shows that at idle (when the car is fully up to temp) Bank 2 post cat O2 is in closed loop mode, while Bank 1 post cat O2 is in open loop mode. A quick read on the internet tells me that cars will go into close loop at idle, and I am guessing the fact that Bank 1 is in open loop means something is off. Will a failed O2 sensor cause this? Or perhaps something more? Much thanks Mike
I would swap the O2 sensors and see if you see the same fault. In general, after year 2000 most car manufacturers uses the post-cat O2 sensor to provide additional emission feedback to the ECU. Prior to 2000, the post-cat 02 sensor was mainly used to gauge cat efficiency.
Ok I just did some additional diagnostic (before switching the actual o2 sensor because they are a major PITA to do on the f430, having to remove the airbox etc). At idle: Bank 1 cat temp = -50C, precat sensor in Close Loop, postcat sensor in Open Loop Bank 2 cat temp = 0C, precat sensor in Open Loop, Post cat sensor in Closed Loop So now I am thinking maybe it is my Bank 1 Thermocouple sensor that has failed, which is why Bank 1 postcat o2 is stuck in Open Loop... not being activated due to the car perceiving the cat is not up to temp and and giving me the Bank 1 o2 sensor stuck on lean CEL. But also brings up the question on why the Bank 2 cat temp reads as 0C?
Hmmm so I swapped the thermocouple on both side because that was the easiest. But still getting the bank 2 postcat o2 stuck on lean error. Sent from my iPhone using Tapatalk
I'm not familiar with the xdiag pro 3 reader. Do you trust it? Can you use another make/brand reader to verify the xdiag pro 3 readings? What's your fuel trims?
Hi mello, is there another term for fuel trim, and what is the normal reading (output) of fuel trims? I am thinking the same... not sure if the reader is giving me the proper reading. My universal OBD2 reader that I am using to read my CEL is giving me a voltage reading of .45v for the bank 2 o2 sensor, yet it tells me it cannot (not supported) to read bank 1 o2 sensor. Between this, and that I am also getting weird readings on the xdiag app relating to exhaust temps (even though swapping the thermo couple did not move the error onto the other bank) makes me think both readers are only reading partial info. Also the xdiag app does not read the voltage from the postcat o2... or it doesnt have that field. I am super confused with it. I think the next step I have is to take out the o2 to test it, and swap sides to see if the error switches banks.
There's no point in using a diagnostic tool that you cannot rely on with confidence. It'll just send you on a wild goose chase. You switch the thermcouples, but have you consider switching the thermocouple ECU to test? On my 360 Spider, I get around 1-5% on the short fuel trim and around (+/-) 10-15% on the long fuel trim, depending on how hard you drive the car. The O2 sensors affect the fuel trims.
Got it, I will read more about the fuel trim and see if I can use it to do diagnostic. On the 430, I believe they have done away with the thermocouple ecu, and it is integrated into the motronic ecu that controls everything else (ignition, etc) according to the owner's manual.
In post #1 you say: I keep getting a CEL for Bank 1, post cat O2 sensor stuck on lean error code. In post #4 you say: But still getting the bank 2 postcat o2 stuck on lean error. A lean error code is a result of the post O2 sensor going out of bounds on a lean condition. The pre O2 sensor generally manages fuel trim and the post sensor reports on whether it the fuel systems and catalytic converter are working properly. You can actually watch what the fuel trim is doing on each Bank to have a reference point if you have a reliable OBDC diagnostic reader. -50C unless you live in outer space is a bad reading as well as 0C..... for Temp.... not sure what is up with the tool you are using. So most people blame the 02 sensors for throwing bad data to the ECM and replace them. I'm pretty sure that there is an upstream problem possibly an injector or exhaust leak that is causing the O2 sensor to throw the code. The easiest way to tell is to have a reliable diagnostic tool.....without it .....we are just guessing.
Good catch. I think post #4 was a typo. Good info on fuel trim. I will do more research on it and use that as a basis for my next test when I get back to the car again Sent from my iPhone using Tapatalk
I will check for those, thanks. Mainly need to learn a bit more about fuel trim so I can see what to check for. I highly doubt it is a bad MAF or cracked headers as I installed new headers and cat bypass earlier this year and have been running with a low cat efficiency CEL on both banks. Recently installed mini cats on my o2 sensor and started getting this stuck on lean CEL but only on one bank. Freak occurrence aside I feel like whatever was most recently touched is most likely the point of failure.
Follow up to the ongoing diagnosis: Turns out both post cat o2 sensors are reading stuck on lean. I took them out, took off the o2 mini cats, swapped left with right but without the mini cats, and now I'm getting low cat efficiency on both sides. So both are working fine. Either the mini cats are working too well or they weren't screw on tight enough (I was able to twist off the o2 sensors initially by twisting with just two fingers). I'll put on the mini cats tighter this time and test again. If it's the mini cat scrubbing too clean I gotta bite the bullet and get a tune. Also, fuel trim looks okay. Short term fuel trim bounces from -3% to +5% but most of the time hovers around 0%. And long term fuel trims indicates around 0.8% so the engine is not trying to run richer or leaning the fuel mix? Sent from my iPhone using Tapatalk
So without the mini-cats.....you get an expected (since you removed the original catalytic converters) low cat efficiency code and fuel trim is ok. When you use the mini-cats you get a lean condition on both banks and the low cat efficiency codes go away. Is that right? Unfortunately, it just comes down to the O2 sensors behind the mini-cats are not replicating the signal the ECUs are expecting. Perhaps other owners who have had more experience with them can provide a better perspective. From my perspective, most of the O2 extenders and mini cat systems seem to be hit or miss when used on a Ferrari. They create dead air since the O2 sensor is actually out of the exhaust stream. That means that the air it is monitoring is likely superheated and has too much O2 which in turn translates into a "lean" code. I would be far more concerned with lean/rich codes than I would be about low cat efficiency codes. Lean/Rich codes are managed by the ECU and the fuel system. The low cat code is just indicating the catalytic converter is not doing it's job. I'm still a little puzzled why you pulled off the original catalytic converters in the first place. Unless you frequently track the car....I'm not sure you would see a difference.
Your first paragraph's summary is exactly right. The more I think about how cats and o2 sensor works, the more I feel like you're right. Its just not worth the hassle. Wish I gave it this much thought when I bought these mini cats. As for the lean / rich code, I dont think it is too much concern as they are only triggered by the post cat sensors. If it senses the cat is going bad it will run rich to preserve the cat with lower the exhaust temp, if it senses it is running lean it will run richer to see if the post cat sensor will respond. Either way the car will run richer which means you just lose some power and wont be working at 100% efficiency. Whether the car runs rich or lean in this scenario is controlled by the ecu, and the ecu will not run the car beyond a pre determined safety parameter, it will just give up and go back into an open loop and throw a CEL if it is beyond what adjustment it is allowed to make. What will really cause issue is if the car runs rich or lean and is not caused by the ecu, and that is the risk as that could deviate further until it becomes harmful to the engine. As for doing the cat bypass, I originally wanted more noise so I went with it, it was working fine until my OEM headers cracked and I had to go with aftermarket headers with no precats. I love how loud and obnoxious the car sounds, given that I ride the subway / take the bus every day and that the car is parked in another state, the added noise level feels literally like the automotive equivalent of taking cocaine on the few times I get to drive it each month.
Concluding post on this matter: Tested it with the o2 sensor and mini cats screwed on tight, still getting low cat efficiency codes. Good news is that after these several rounds of trouble shooting, all the o2 sensors + thermocouples work, and learned a great deal in the process of how these things work in conjunction with the ecu.
I am experiencing bank two precat not coingout of open loop. Does anyone know how this was solved for this members car.