Originally Posted by jmoryl
I've made some progress. After installing a new front sensor and getting the same codes, I'm down to one code, P0141, after several read/clear/CEL cycles. Funny how these things work sometime. So it looks like I'll just replace the rear sensor now. The SOB is bent, so it looks like it will be a hassle to remove - anyone have any experience to share?
This is common.
When you bottom the header out it flexes enough to smash the sensors against the engine/halfshaft. This bends the sensors and shorts the heating element to the body of the sensor. This will blow the fuse that is common between both sensor's power circuit and you end up with heater circuit codes.
When the PCM is bad it sets codes for both sensors all the time. So... if you're only setting the code for the rear - the heater element/circuity inside the sensor is toast. Replace the rear sensor and you should be good to go.
Make sure you bring your old sensor into the parts store to match it up. All parts stores categorize 02 sensors based on the element design and pigtail harness length. Autozone, Orielly, Napa, CarQuest and Pep Boys all show the incorrect length of pigtail for the rear sensor (at least for my SVT). I had to ziptie a crapload of extra harness because I couldn't find a direct replacement...