I have a 523i that has failed on emissions! I have tried to scan the car with the OBD port in the engine bay but cannot get the diagnostic tool to communicate with the the car, but that's another problem lol
Basically I was advised to "hook her up" and find out which (if any) O2 sensor/s is causing the engine to run rich.
I removed the front pre sensor for visual inspection (and to check I order the correct one/s) and tbh it's not looking too bad but then appearances can be deceiving.
So the question is.....are the post CAT and pre CAT O2 sensors the same sensors or are they different, I only removed the front (easy one) today and need to raise the car for the 2nd sensor and look at the others for removal.
Also, does anyone have any other tips on advise on why she would fail the emissions test.
Thanks in advance.