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Will a new PCM fix my issues?

StephWinters111

New Member
Joined
Mar 8, 2022
Messages
1
Location
Conroe, TX
Hi everyone. I am new here.... I'm having issues with my Jeep and I need some advice. First... I'm in Conroe, TX (outside of Houston). She's a 2002 Jeep Wrangler TJ, X series. 4.0L 6 cylinder, manual transmission. I've had her since 05. In 2018 my engine blew. I had a 2005 engine installed (about 65K on that engine) and had issues starting her. My computer wasn't recognizing the sensors, so we changed those to 02 ones and she started, and soon after, back on the road. Since then I have gotten the oil changed regularly, and haven't done anything but drive to and from work. No off roading, nothing like that. This past November, she started hitching and lurching while I was driving. My mechanic wound up putting a new cam sensor on and a new synchronizer. She was fine after that, until beginning of January. Check engine light came on after the engine started lurching and hitching again. The code was P0340. Different mechanic put another new cam sensor on, and I think ignition coil. Misfiring so they had to put a new spark plug in. Then.... she drove fine. Until Feb 24th... so little over a month later. Again... lurching and hitching of engine and same P0340 code. Took it back to the place I took it to in Jan. This time, the mechanic had no clue and all but shrugged when I asked questions. Now.... he did put ANOTHER cam sensor on it, even tho I told him, with my own research that it could be a circuit issue and not the sensor itself. He said he didn't have the right stuff to do a full diagnostic. So... towed to a different shop, this mechanic had worked on my Jeep in the past. He said the codes were now P0340 and P0320. He checked wires, said they looked fine. He set timing off by 10 degrees, drove her 3 times and said she was good. I got a ride, went to drive out of the parking lot and the lurching happened again, engine rough and check engine light came on. I checked the code and this time it said P1391 Manufacturer Control. Left Jeep there.... and mechanic said on March 3, that she's acting up. Drove it, was ok. Then checked cam sensor wiring...tried to start her to pull her to another spot and started acting up again.... idling badly, etc... I do need to check if he did in fact, get the cam sensor in but I assume he did. He thinks it could be my computer. And they are few and far between. So, I just would like to know if this has happened to anyone else and if it's fixable. I am at my wits end, I'm almost ready to give up but she's my only vehicle.
 

Lou

Jeepin with Jesus
Supporting Member
Joined
Jun 16, 2016
Messages
2,578
Location
Long Beach
The wiring harness can rub on the right rear corner of the head. The cam sensor signal wire is in that part of the harness. Sounds like your wire is shorting onto the head. Once they get in there and work on it, the wire is no longer shorted, only to return later.
 
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Lou

Jeepin with Jesus
Supporting Member
Joined
Jun 16, 2016
Messages
2,578
Location
Long Beach
You have to remove a shit ton of tape and loom to even see this.

2C6AFAC9-53C4-4B34-AED2-55DE15A00129.jpeg


E8AF4740-E2FC-4C23-BCE3-DC2C6F6FA718.jpeg
 

machoheadgames

LED turn signal club
Supporting Member
Joined
Jan 21, 2021
Messages
958
Location
Dallas, TX
I would dig into the back of the harness like Lou said and see if you can find a short. Common issue on TJs. If not that, I could see the PCM being bad as a possibility, though that year is not commonly known for pcm issues. Even so, it is a possibility.

I’m down in Conroe every so often but unfortunately not soon enough that I can offer any real in person assistance.

I would definitely check the harness where it turns the back corner of the engine though. Common area where chafing and shorting occurs.
 

RMETeeJay

TJ Enthusiast
Supporting Member
Joined
Sep 30, 2019
Messages
933
Location
CO, USA
Wondering if the ECM mismatch could be a factor. Several sensors changed between 02 & 05. See if you can source an 05.
 

thedustyboot

From the great white north eh?
Supporting Member
Joined
Feb 20, 2022
Messages
53
Location
Powell River, BC
@RMETeeJay @machoheadgames @Lou @StephWinters111

97 TJ here with the four angry squirrel flavor. When I purchased my Jeep (AX-5 trans) the seller stated it had the PCM out of another TJ with an Automatic transmission. Since the day I purchased it I've had an intermittent issue where the engine with sputter/stumble briefly when driving. After reading @StephWinters111 issues she was experiencing it appears I may be in the same boat even though mine happens maybe only once or twice during each driving session.

It is possible there's a bad connection or short somewhere, hitting bumps/potholes offroad with enough speed will cause the engine to stumble briefly as well.

It has a re-manned long block with about 13,000km on it now. I do not know the year of the jeep my PCM came out of and an oem PCM on Rockauto is going to run me just over $300 CAD.

Any thoughts folks?
 

RMETeeJay

TJ Enthusiast
Supporting Member
Joined
Sep 30, 2019
Messages
933
Location
CO, USA
First, you should start a new thread instead of burying it here.

Before you go down the PCM road, I'd do a full tuneup (cap, rotor, plugs and possibly wires if they test as high resistance). Download the FSM from here and look up the page with all of your ground connections. Inspect all of them, and R&R anything that looks crusty or suspect. When engines get swapped, sometimes the factory grounds aren't as solid as they should be.

Check for stored codes and report back if you find anything: https://www.offroaders.com/tech/jeep/TJ_diagnostic_codes.htm

You can also try moving your harnesses and wiring around while your fully warmed up engine is running to see if you can replicate the stumble.
 

thedustyboot

From the great white north eh?
Supporting Member
Joined
Feb 20, 2022
Messages
53
Location
Powell River, BC
First, you should start a new thread instead of burying it here.

Before you go down the PCM road, I'd do a full tuneup (cap, rotor, plugs and possibly wires if they test as high resistance). Download the FSM from here and look up the page with all of your ground connections. Inspect all of them, and R&R anything that looks crusty or suspect. When engines get swapped, sometimes the factory grounds aren't as solid as they should be.

Check for stored codes and report back if you find anything: https://www.offroaders.com/tech/jeep/TJ_diagnostic_codes.htm

You can also try moving your harnesses and wiring around while your fully warmed up engine is running to see if you can replicate the stumble.
Appreciate the info good sir 😄 I'll dive into that late next week when I'm home from work. Would you recommend starting a new thread with all my findings? I can tag you in the new thread after my investigation if you like.
 
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Roccrawler3

Member
Joined
Jun 11, 2019
Messages
25
Location
lake arrowhead ca.
Hi everyone. I am new here.... I'm having issues with my Jeep and I need some advice. First... I'm in Conroe, TX (outside of Houston). She's a 2002 Jeep Wrangler TJ, X series. 4.0L 6 cylinder, manual transmission. I've had her since 05. In 2018 my engine blew. I had a 2005 engine installed (about 65K on that engine) and had issues starting her. My computer wasn't recognizing the sensors, so we changed those to 02 ones and she started, and soon after, back on the road. Since then I have gotten the oil changed regularly, and haven't done anything but drive to and from work. No off roading, nothing like that. This past November, she started hitching and lurching while I was driving. My mechanic wound up putting a new cam sensor on and a new synchronizer. She was fine after that, until beginning of January. Check engine light came on after the engine started lurching and hitching again. The code was P0340. Different mechanic put another new cam sensor on, and I think ignition coil. Misfiring so they had to put a new spark plug in. Then.... she drove fine. Until Feb 24th... so little over a month later. Again... lurching and hitching of engine and same P0340 code. Took it back to the place I took it to in Jan. This time, the mechanic had no clue and all but shrugged when I asked questions. Now.... he did put ANOTHER cam sensor on it, even tho I told him, with my own research that it could be a circuit issue and not the sensor itself. He said he didn't have the right stuff to do a full diagnostic. So... towed to a different shop, this mechanic had worked on my Jeep in the past. He said the codes were now P0340 and P0320. He checked wires, said they looked fine. He set timing off by 10 degrees, drove her 3 times and said she was good. I got a ride, went to drive out of the parking lot and the lurching happened again, engine rough and check engine light came on. I checked the code and this time it said P1391 Manufacturer Control. Left Jeep there.... and mechanic said on March 3, that she's acting up. Drove it, was ok. Then checked cam sensor wiring...tried to start her to pull her to another spot and started acting up again.... idling badly, etc... I do need to check if he did in fact, get the cam sensor in but I assume he did. He thinks it could be my computer. And they are few and far between. So, I just would like to know if this has happened to anyone else and if it's fixable. I am at my wits end, I'm almost ready to give up but she's my only vehicle.
Crank sensor.. Or IAC idle air control
 

Mik

Member
Supporting Member
Joined
Sep 10, 2018
Messages
46
Location
Spring
You have to remove a shit ton of tape and loom to even see this.

View attachment 314212

View attachment 314213

Thank you will try this as well. Spring,Texas and running into the same issues 05 i6 and this does drive you crazy trying to figure out the exact problem. If you find that local expert please share. Mine will start then conk out one day then the next day I can run it idle for 30 min no problem.
 

Krusty_tub

Member
Joined
Apr 23, 2022
Messages
92
Location
Ct
I would look at a engine management wiring diagram and prove out those cam sensor circuits before going any further. Isolate them by disconnecting the pcm and distributor, use a DMM to see what they read, usually under 4 ohms, however, that only tells you the circuit is intact.
Once confirmed, I then check that circuit for a short to ground, should be greater then 10k ohm or OL.. If less then you probably have a wire rubbed through and touching a chassis ground/engine.
If that passes.. then supply a independent power source through each isolated circuit at a time and run a test light on it, if it lights up bright, Great! Dim... problem circuit, no light at all, you probably just burned off the last thread of wire.. 😆

These mechanics sound like they are just firing parts at it... the one who said "didn't have right tools" at least he's honest 🙄 🤣

Don't go back to them unless you need something simple like some brake pads or washer refill.
 
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