So I still have a intermittent P161/160 code that pops up randomly. This is right bank rear. The UG reads in the middle which is a default at .450 and moves a little off that sometimes but not normal like the other three. So it gets some signal I guess. This does not appear to have an impact on drivability. The O2 sensors are OK and have been swapped left to right etc. The wiring has been repaired at some point and the harness has correct continuity from the pin connector at the ECU to the plug at the O2 for all four wires. I could still check for resistance but not sure how to do that.
With that said I am thinking it might be ECU. I know I can buy a used one and swap / reprogram with a Nanocom and I might try that but was also curious about the repair route. Anyone done it? If so who did it and how did it work out. Plenty advertise it but I don't know who is reputable or just taking your money.

 

Before I would send it out for repair I would make 100% sure the problem is the ECM. Measuring resistance is the same as measuring continuity but instead of listening for a beep you look at the meter and read the numbers.

I've been having persistent O2 codes as well and it turns out my cats are cracked leaking at the seams. When I pulled the y-pipe and prepped them to weld I realized the honeycomb inside is broken and rattling around. I was about ready to pull the ECM and look for corroded connections and such. I'm hoping new cats will clear up my issues.

 

My cats are suspect for sure. I have isolated a cold start rattle to the drivers side cat that seems to be getting worse. P0161/P0160 are not cat specific codes but could be related I guess. They are LR cats and could be original.

 

Anything that's been rewired is always suspect. I've seen some crappy jobs that look crappy and some crappy jobs that were polished up real nice. What do the connections look like, electrical tape, heat shrink, butt joint, wire nut, or worse.?

Cats going out on this truck seem to give all kinds of fishy codes or no codes from what I've read. One of the normal codes that leads to Cat replacement is p0420 and p0430 catalytic inefficiency. Unfortunately my codes are o2 sensor no activity codes, even though an OBD scanner can see activity on both upstream o2s. But at 200,000+ miles I felt it was the right move to replace the cats.

 

The re-wire job doesn't look too bad. It's redone all the way up to above the transmission where I can't see it merge with the factory loom that tees off on the firewall above and behind the engine. My crime scene analysis is that the front driveshaft cut loose taking the right o2 sensor pigtail with it. This maybe wrapping up and stripping it back further causing the wiring to need replacement all the way back up top. Most likely the driveshaft fail (before my ownership) led to a transmission removal / rebuild as the pan looks new and it has some marks on the bell housing. Also dents on the floorboard. Then the repair was done to the O2 sensor pigtails while everything was removed. Only the rear right has a code. Attached is a video of the UG. B2S2 is usually stuck at .450 +/- .010 while the other fluctuate normally. So it does get some sort of signal I guess.