From time to time I will get a cat inefficient code out of bank 1. I looked at the voltage on the 4 O2 sensors, and they are not mirroring each other. But I can see a bit of an issue with the one cat. It is still working, but maybe not as well as it could.
My question is does the down stream O2 reading have any effect on fuel trim levels? I know on most cars guys would always tell you that the down steam was just because of government mandates but would not effect your car running. Now on newer Chryslers the down stream O2 talks to the up stream and they talk to the computer.
Just not sure if Cadillac did that. This is on my 06 STS 4.6