Do the two rear o2 sensors do anything to the motor or just tell the pcm if the cats are working?

 

Bump

 

The front O2 sensors monitor a/f ratios. This keeps you from running rich/lean. It does this by sending the a/f info to the PCM, and the PCM adapts fuel trims taking into account temperatures, MAF reading, etc. Messing with the front O2 environment without proper tuning can affect running. The rear O2s just monitor cat function, they'll trigger a CEL, but don't affect the motor.

 

Ok thanks thats what I thought