Repeating O2 Sensor Codes

[Contra]

For some reason I can't get a pre-cat bank 2 O2 sensor to last more than 3,000 miles. I'm starting to think maybe something else is causing the codes.

I've replaced the bank 2 pre-cat O2 sensor at 74.5k miles and again at 77.5k. I'm currently at 78.8k and I got the following codes:

274B: DME Oxygen sensor pump current calibration error before cat. converter bank 2

27B0: DME Secondary air system flow rate, bank 1

27E1: DME Oxygen sensor after cat. bank 1, signal

After resetting the codes, only 274B came back.

I can replace the sensor again for free thanks to FCP Euro, but I feel like O2 sensors should last longer than this.

Anyone had anything similar?

Car Info / Relevant Mods:

2008 E92 Coupe
RKP Street X-pipe
Corsa Rear Exhaust
Macht Schnell Underdrive Pulleys
Macht Schnell Intake

[munstro]

I had a similar issue, dealt with by my shop and then the dealer. My shop methodically worked through the issue, replacing the o2 sensor twice, worked through the coding, and eventually replaced the DME, of which were only temporary fixes. It then went to the dealer who replaced the engine wiring harness, but then the car through another code for the catalytic converters. After replacing the x pipe with a brand new one from Germany (the wiring harness also came direct) the code has been gone ever since. When all was said and done I’m not sure if it was the bad cats causing the issue all along. It was an expensive and time consuming journey, but well worth it. For what it’s worth there is another thread in here somewhere of another owner having the same experience as mine.

[Contra]

Originally Posted by munstro

When all was said and done I’m not sure if it was the bad cats causing the issue all along.

If the cats were bad, it should be fouling the sensors post cat, right? My pre-cat sensor has been the only consistent code I've gotten and I haven't had any codes regarding the cats specifically.

Recently I did notice a weird drone / heavier engine load sound while driving through heavy rain when I hit a small puddle of standing water. My current theory is I have a failed / missing exhaust gasket or something allowing water into the pipes.

I read a thread where somebody was experiencing something similar and it ended up being the donut gaskets at the header to x-pipe connection. Not sure if this could relate to my car eating O2 sensors.

[munstro]

I wish I could help you more, however working on M cars is far from my specialty. I spent lots of time searching threads trying to find something that may help as far as advice for my mechanic. I do know my shop did thorough checks for exhaust leaks, and I can say during all the weirdness associated with my CELs my car never ran strange at all. In fact my tech said on several occasions “there’s nothing wrong with this car”.

[Contra]

Originally Posted by munstro

I wish I could help you more, however working on M cars is far from my specialty. I spent lots of time searching threads trying to find something that may help as far as advice for my mechanic. I do know my shop did thorough checks for exhaust leaks, and I can say during all the weirdness associated with my CELs my car never ran strange at all. In fact my tech said on several occasions “there’s nothing wrong with this car”.

Thank you for your input. Fingers crossed my issue is easier to track down and I don't end up messing with the DME and wiring harness.

[munstro]

OP have you figured this issue out?

[Contra]

Originally Posted by munstro

OP have you figured this issue out?

Haven't had time to get the car in the air yet. Been a busy month for me. Likely going to have a look sometime next week. I'll definitely update the thread with findings.

[munstro]

That would be great. It seems many of these o2 sensor threads don’t go anywhere and it seems to be an issue for some.

[kimiraikkonen]

Originally Posted by Contra

Haven't had time to get the car in the air yet. Been a busy month for me. Likely going to have a look sometime next week. I'll definitely update the thread with findings.

Maybe check to see if you dont' have any problem with your donut gasket (the one that connects from the manifold to the pre-cat exhaust inlet. You might have a small intermittent leak that is occurring under load or various driving conditions.

I had some wacky engine DME codes and thought it was the O2 sensor, but turns out I had a missing donut on the bank 2 pipe. Folks werent' sure if it had disintegrated or if it was missing due to a bad install at a shop when I put on the MPE exhaust.

[Redd]

Originally Posted by kimiraikkonen

I had some wacky engine DME codes and thought it was the O2 sensor, but turns out I had a missing donut on the bank 2 pipe. Folks werent' sure if it had disintegrated or if it was missing due to a bad install at a shop when I put on the MPE exhaust.

The donut gasket has a wire mesh core that is exposed as the graphite disintegrates. If your exhaust didn't have that thin wire mesh then likely it was an installation problem and they didn't put the donut gasket back.

[Contra]

So update after getting the car in the air:

I stupidly thought the bolts for the header to X-pipe connection were torx and not e-torx, so I didn't have the correct socket to remove them. I couldn't check the donut gasket.

However, I did find that my exhaust had loose clamp likely causing an exhaust leak.

My car has the RKP Street X-pipe which required cutting the OEM X-pipe just after the primary cats and slipping the RKP pipes over the cut section. The clamp around the OEM cat to X-pipe slip connection was loose enough that I could turn the cat with my hands.

I tightened the clamp and reset the service engine soon light, but the code came back. I'm thinking maybe the exhaust leak could have caused the sensor to die.

I ordered some e-torx sockets and a new O2 sensor and I'll update again when I have time to work on the car again.

[Contra]

Update 2:

So I got the correct socket and took the cats off. The RKP Street pipe is slip fit over the cats, so I was able to undo the bolts and O2 sensors and wiggle the cats themselves off of the headers.

No donut gaskets at all. I replaced the O2 sensor already, but I'm going to order donut gaskets and put them in. Fingers crossed my sensor lasts longer than 3k miles this time.

[jucheng]

Hey OP,

any further updates? My car, like yours, is getting the same 274B code every 1k-3k miles. Replacing the pre-cat O2 sensor is not fixing it and the code keeps coming back...

Hoping you or someone has figured it out!

Cheers

[Contra]

Originally Posted by jucheng

Hey OP,

any further updates? My car, like yours, is getting the same 274B code every 1k-3k miles. Replacing the pre-cat O2 sensor is not fixing it and the code keeps coming back...

Hoping you or someone has figured it out!

Cheers

It hasn't come back since I last posted. Things I did:

1. Replaced header to X pipe donut gaskets.
2. Removed X pipe and tightened all the bolts between the sections (this doesn't apply if you have an OEM X pipe)

I still for sure have a small exhaust leak on the passenger side OEM cat-to-X-pipe slip fitting, but that side's sensor hasn't ever thrown a code.

Hope this helps!