Got it sorted out, but wanted to put some mileage on before posting. This might help someone in the future...
P0122 and P0123 CELs in my 2000 Jeep Cherokee XJ
Timeline:
- Was on the highway and started having the transmission hunt and jerk like someone was stabbing the throttle, transmission downshifting. Got to the point that once I was up to speed I could maintain speed for the most part.
- Had my scanner with me and pulled codes, only had p0122 code. Found a tps sensor local and swiped that up, swapped out and seemed to fix my issue for 10 or so miles(foreshadowing), but then came back.
- toughed it out and limped it for the rest of my driving around that day.
- got it home and swapped back to the original tps. Did sweeps and couldn't find anything wrong that was out of spec. Pulled clockspring plug to eliminate 12v interference possibility. Could not find any open shorts in wire harness through testing, did not disassemble harness to visually inspect. When vehicle was cool, nothing seemed to be wrong.
- each time I test drove, it would be fine until approximately when it would come up to temp, or there abouts. Mind you, this is Michigan summer, so fairly warm. This was within 2 miles of leaving the driveway each time and i would get a p0122 code. Seemingly randomly i would also get the p0133 code for tps voltage high.
- Got home after a short test drive and had it to a point where the CEL would not clear, so I had something I could work with. I started unplugging other 5v sensors to see if I could get it to do anything MAP sensor did not affect, but the IAC valve did. So i picked up a new one of those too.
- CEL still came on during test drive, but could not get issue to repeat in driveway. Had the hood up and was shaking harnesses. Could not get a code. I had it idling in driveway for 25 minutes or more without fault, and was shacking and playing with the throttle to try to get it to throw a code.
- Eventually came to the conclusion that I think there was a weak solder joint in the PCM causing the 5V sensor wire to fluctuate, or the 5V feed to fluctuate once it got warm. I didn't particularly want to heat up the pcm and possibly damage it to see if i could mimic the failure, so I ordered a replacement refurb off of eBay. Luckily I asked a few of the sellers and found one that I wanted to do business with as they did not charge a restocking fee and did accept returns if it didn't fix my issue. Got the computer, swapped out and did a reset, initial 10-15 mile test drive with no issues. drove it about 70 in the morning and afternoon commuting back and forth to work taking the country highways was in the high 60s in the AM and high 80s in the PM. Going to call this problem fixed. Want to put some more miles on it when I'm not in a big rush for anything to build confidence, as it is a pretty annoying issue to deal with away from the driveway or am on a timeline.
unrelated I also found my external trans cooler was leaking slightly so I replaced that as well with a new Hayden unit.
Glad I put carpet back in, now I can actually drive it without almost burning my feet off on the floorboards/trans tunnel. Would have expected a slightly better insulation value from the sound deadener, but it is what it is. Went with the higher mass backing. Jeep is pretty quiet now inside the cabin aside from the hum of the MTs.
Noticed that the throttle cable was pretty loose, so might righ that back up a fuzz to get back to 100% useable throttle. Next things up on this would be to wire up the gauges on the center console, and get my CB wired in to my custom overhead console mount.
I'd like to pick up a Tauler Jack for it too and find a nice spot to have a permanent high lift jack on board.
