Bad O2 Sensors

[GuidoInc]

I have a 96 Q45 100K miles. I had the front O2 sensors replaced. The trouble codes I am getting are PO141, PO161, PO135, and PO155. These are showing problems for all O2 sensors. My quesion is would having bad rear O2 sensors make the front O2 sensors report a bad code? Also, where can I get the rear O2 sensors at the best price? I've seen the listed for the front but not the back.

Thanks all.

[Q45tech]

The rear O2 are out of phase with the front, a more + on the front usually is more towards lean [zero] on the rear and the converse. There is also a time lag as the catalysts does its job.

The rears usually fail first but by 100k it is time to replace all!