Fault Codes

[darrtracing]

My 1997 M3 is throwing the following codes during each drive:
-Cb: Oxy sensor control limit, Cyl #4-6
-E4: Oxy sensor adaption limit, Cyl #4-6

I assume this means I have a bad O2 sensor.

Does anyone know if this is post or pre cast and which bank is 4-6? (front or back)

Thanks.

[darrtracing]

Any thoughts?

[JhwShark]

In a straight 6, cyl 1# is the front, so 4,5, 6 are the back. I do not have your model only lots of prior ownership of 3's and 5's.

Jon