I was having the same O2 codes for several years that were not fixed by the previous owner replacing all the O2 sensors. One of the pre-cats finally catastrophically failed on the highway. Its internal parts blew downstream and plugged the main cat enough to drop my top speed to 4-5 mph in about a quarter mile. Replacing all three cats cured all the O2 sensor codes and the engine ran a lot better afterwards too.
@Jerry Bransford Jerry which O2 codes were you getting?
I have all 4 O2 Heater sensor codes ‘ O2 Heater control Low”, P0031, P0037, P0051, P0057 and debating whether to try the PCM or not. Since these codes pop up immediately after ignition on ( not started) and a code clear, I’m thinking that would not be caused by cats, but I’m no expert on cats.
This all started with my earlier no start problem , resolved by correcting brokengrounds on G105 , RH side of engine block. But the above O2 codes remain.
My next step is to just get the 2 new upper 02 sensors in, the lower ones are newer. Then do more wire harness voltage / ground testing on each 02 plug on harness. Will be a lot easier to use an old O2 sensor plug to test harness Plugs.
Just trying to avoid cost of new PCM if not needed.
@skrelnik If I followed your history correctly. Your low O2 heater codes were corrected with new PCM, but when you put back original PCM, they did not reappear? That one makes me wonder if there’s anything else, other than possibility of PCM being intermittent.
Jeep is an ‘06 TJ, manual, ~ 75k miles.