madduc

Hello Audi Enthusiast,

Like to know if any other RS4 owner having same problems with there o2 sensors? Car has only has 37,000 miles and I replace (3) 02 sensors; bank 1 sensor 2, bank 2 sensor 1, and bank 2 sensor 2 the two downstream problem was with heater control circuit and pre-cat was stuck open running rich. I just don't understand why sensors going bad so quickly.The car is modded and post-cat sensors are re-locate back of the cats to prevent check light so anyone has suggestion or comments would be much appreciative.

Thank you,

madduc

Quess nobody has this problem?

silverRS4

First of all, is a dealer replacing them because the sensors have failed diagnostics and are actually bad or are you replacing them because you keep geting DTCs stored in the ECM's?

Relocated downstream sensors don't always "fix" the catalyst efficiency CEL's and modified airboxs and/or inlet ducts can cause the mass air reading to be incorrect, leading to out-of-range O2 correction and more CEL's.

You are right, O2 sensors typically just don't "fail". The car is modified. Ok. I would say the problem with O2 sensors probably wouldn't be happening if the car was stock. Whoever modded the car, needs to either:

A) Figure out exactly whats happening rather than just putting in new sensors. Is the wiring to all of the sensors OK? If that and other normal troubleshooting procedures get nowhere..
B) Get the car back to stock and start over one mod at a time until you find the culprit.

Reggie

SilverRS4 is right - The relocation of the O2 sensors is not the right thing to do. Either return the car back to stock or return the O2 sensors back to the original location and get a chip flash that will ignore the second O2 reading after the downpipe.

I doubt that the amount of hp increase with this car is worth the removal of the cats