Limp mode..

epadams91

New Member
Joined
May 25, 2023
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5
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Tennessee
Hey yall, i have a 2012 wrangler unlimited sport and she has 219xxx miles. Limp mode started a little over a year ago when the clockspring light came on then caused traction control light. At that time it threw p0390 and p0349 which are cam codes p0335 crank code and an 02 sensor code. We changed all of those and it didnt help. Took it to dealership they replaced all of those again along with fixing the clockspring and told us we needed a new oil pump. Got about 10 miles from the dealership CEL and traction control light came back on and went back into limp mode. We changed the pump along with timing gears which was broken at the bottom of oil pan(no it didnt jump time). We changed all 4 wheel speed sensors along with pigtails didn't help. At that time we could always turn it off then back on and could go a few miles before it would go back into limp mode. Fast forward to April of this year we got all of these codes P0390, p0349, p2638, c123f, c121c, u0100, u140e, c2202, u0401, b1638, b1634, u0184, b1630, b162c ..it started going straight to limp mode as soon as we would crank it. Since then we have replaced every sensor the jeep has, checked all grounds and wires, new alternator, new throttle body, new idler pulley, new spark plugs, new coil packs, new pcm and just last night changed the tipm. Even with the new pcm its still pulling the exact same codes. Along with another oil change. None of that has helped. We are at a complete loss. We have taken it to a total of 5 different mechanic shops along with the dealership and noone can help us. We also done a live feed to check the cats and all of that was fine too. Next thing we are changing is the injectors and after we do that we have no idea what else to do. Ball joints wheel bearings and everything under the jeep is fine. We even took my 22x14s off and put my 18x9s back on to just see if it would help.
 
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That's a lot of part replacement you've detailed. One, all encompassing sort of question: with each part replacement did you:
1) use OEM replacement parts?
2) reset the ecm so it could learn the new parts?
 
The parts came from either oreileys or the dealership. The pcm was replaced and reprogrammed after the majority of that work was done but even with the new one it threw the exact same codes.
 
What is the ECM relearn procedure??


 
Thanks. Just did lifters and rocker arms on the driver's side to solve the infamous lifter tick....and there were 3 bad rocker arm. Luckily no cam damage occurred. Put everything back together and start her up and now I have a P0349 and C121C. They won't go away when cleared. Even with the key on, engine off, the code reappears. Gonna try n reset the PCM. If this doesn't work, then I'll start looking for a wiring issue. It's always something these Jeeps!!! 🤬🤬🤬
 
Thanks. Just did lifters and rocker arms on the driver's side to solve the infamous lifter tick....and there were 3 bad rocker arm. Luckily no cam damage occurred. Put everything back together and start her up and now I have a P0349 and C121C. They won't go away when cleared. Even with the key on, engine off, the code reappears. Gonna try n reset the PCM. If this doesn't work, then I'll start looking for a wiring issue. It's always something these Jeeps!!! 🤬🤬🤬

You might also replace the junk factory battery clamps and clean the battery terminals and other grounds.
 
You might also replace the junk factory battery clamps and clean the battery terminals and other grounds.
Already done.... Junk is an understatement. It just seems weird that it's been perfect for over a year now...no issues and now I disturb the engine wiring harnesses and this pops up. I had to remove the cam phasers and also the cam shaft sensor to remove the valve cover. So I probably knocked something loose and now there's a bad connection or no contact. I'll dive BACK into it tomorrow. I swear I'm gonna sell this thing one day.... But I love it too much.
 
We bought a new engine wiring harness knock sensor harness and injector harness. We are putting it in today so hopefully it'll work.
I found that if you use a magnetic pickup tool to remove the rocker arms and lifters (which I did bc a few dropped down in the head) and if you contact the tone wheel that the cam sensor reads, you can essentially erase the pickups that the cam sensor reads and then.....your cams are junk bc the tone wheel is pressed on at the factory.....so that's where I'm at. Wiring is the least of my worries. But good luck with your Jeep. It's always something!! Lol!!
 
Just to let all of yall and anyone else dealing with this know the new engine harness fixed mine! No check engine light no limp mode!! We changed the harness Saturday and have drove it everyday since and she's doing great!
 
Just to let all of yall and anyone else dealing with this know the new engine harness fixed mine! No check engine light no limp mode!! We changed the harness Saturday and have drove it everyday since and she's doing great!


Thanks for the update, maybe post the harness PN in case someone else might need it.
 
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On my 12 the original part number was 68081220AE. The new harness i bought is 68081220AG. I was informed that the two letters on the end could range from AA-AG and still work as long as the numbers are the same.
 
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