Wiring or PCM Problem? - JeepForum.com

 
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post #1 of 14 Old 02-09-2012, 04:47 PM Thread Starter
jwaller89
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Wiring or PCM Problem?

I was driving through Ft. Worth back in September and my coil pack failed on me in the middle of 820. Did my research on here and despite what I found, it turned out to be a bad coil pack. It was fixed and ran great until this past Saturday.

I was riding through town and I lost power. Turns out one of the banks on the coil pack quit firing. Easy fix I thought. I bought another coil pack and put it on in the parking lot of the local Walmart. It still ran like crap. I call my grandfather who's a mechanic and start asking questions, while I'm talking to him, the Jeep dies. I look at the coil, and one of the banks had split open and started arcing on the dipstick tube, and blew my ignition fuse. I had a warranty on the new coil, so I take it back. They couldn't get me another one until Monday. So I leave the Jeep at Walmart for 2 days for the new coil to come in. Autozone says it could be a flaw in the first one so they go ahead and order me a new one. I put the new one on Monday. It still runs like crap. So I have a wrecker take it to my grandfathers mechanic shop.

He worked on it until this morning and couldn't find anything wrong. He even replaced the coil again. The one I put on in September had a warranty through Napa and he tried it and no luck. I had him send it to the Jeep dealership this morning. They have been working on it all day and can't get their diagnostic computer to connect to the PCM. I'm thinking it's the PCM going bad, but they think I had a short in the wiring that's causing the PCM to malfunction. They want to replace the ignition wiring harness AND the PCM. I told them to wait before they do anything else to it.

I want a second opinion from you fine fellows. What do you think I should do? Let them replace one thing at a time, or go ahead and let them replace both?


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post #2 of 14 Old 02-09-2012, 04:50 PM Thread Starter
jwaller89
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Also, 117xxx miles if it matters.

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post #3 of 14 Old 02-09-2012, 08:53 PM Thread Starter
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Bump for the night crew.

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post #4 of 14 Old 02-09-2012, 11:40 PM
Andrew_02TJ
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If those technicians are even half way competant they should be able to diagnose if you have a short in your wiring harness. However if that is what they are recommending have them replace the wiring harness first before doing anything with the PCM. If possible after they have done the repair let them keep the jeep and drive it for a couple days so you don't get half way down the street after paying for it to take a crap again.

As a side note it may be cheaper for them just to repair the wiring harness other than replacing it. I find it hard to believe that they can't tell if you have a shorted wire or not though, seems kind of fishy. Then again I don't know the entire story so who knows. Good luck to you though.
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post #5 of 14 Old 02-11-2012, 12:06 PM Thread Starter
jwaller89
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Just heard from the dealership. They started it up this morning and everything was working fine and it was purring like a kitten. No codes, no misfires, nothing wrong with it. I'm puzzled.

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post #6 of 14 Old 02-11-2012, 12:17 PM
Keith_C
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Long shot, but we went thru a similar thing with my Wife's TJ.

Spent $2000 at the dealer and turned out to be a loose connector.

Been fine for over 8 months now.

Here's a few details: http://www.jeepsunlimited.com/forums...ighlight=start
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post #7 of 14 Old 02-11-2012, 02:50 PM Thread Starter
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It won't let me visit the link you provided. My anti-virus is saying there's a trojan on that page. What connector was loose?

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post #8 of 14 Old 02-11-2012, 03:16 PM
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Quote:
Originally Posted by jwaller89 View Post
It won't let me visit the link you provided. My anti-virus is saying there's a trojan on that page. What connector was loose?


It supplies the power to the PCM.



Would not explain the fried coil packs, but I don't see how even a short in the harness would cause that.

I pulled that connector apart and 1 of the contact sets looked like they had been arcing.

Cleaned them up with some electronic cleaner and it's been fine ever since.

Like I said, it's a long shot, but the rocket scientists that work for the dealer couldn't find it.
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post #9 of 14 Old 02-11-2012, 05:35 PM
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Hi all


I am curious what did the dealer say was exact cause? TIA................

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post #10 of 14 Old 02-11-2012, 10:50 PM Thread Starter
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Originally Posted by silver97tj View Post
Hi all


I am curious what did the dealer say was exact cause? TIA................
They have no idea. They just started it up this morning to move it and it was running fine. I told them to keep it a few days to make sure no more bugs show up.

I'll check on that connector Monday when I go back and look at it. Thanks for the tip. Maybe it's something simple like that.

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post #11 of 14 Old 02-12-2012, 02:26 AM
Andrew_02TJ
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A bad connector (especially the one noted above by Keith) would explain an intermitent problem as well as the lack of communication with the PCM. However if you had no power to the PCM you wouldn't even be able to start your jeep, it would crank but not start, and definately not purr like a kitten. The bad connector would also not explain the the blown coil and if it was arcing to the dipstick then obviously you have a short to ground, hence your blown fuse. I am intrigued with whats going on with your jeep, please keep up posted, and also, again best of luck with your problem.
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post #12 of 14 Old 02-12-2012, 06:08 AM
Keith_C
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Quote:
Originally Posted by Andrew_02TJ View Post
A bad connector (especially the one noted above by Keith) would explain an intermitent problem as well as the lack of communication with the PCM. However if you had no power to the PCM you wouldn't even be able to start your jeep, it would crank but not start, and definately not purr like a kitten.
My Wife's Jeep would run fine most of the time. Then all of a sudden, no start,

That's what made it so crazy. This went one for close to a year.
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post #13 of 14 Old 02-18-2012, 10:03 AM Thread Starter
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I found the problem. I died on me last night heading out of town to a concert. I was pissed to a point I couldn't describe. I pulled over on the side of the road and raised the hood to take a look. I first start checking the wires coming from the coil. Couldn't find nothing, so I cut the harness open going to the PCM. I found that one of the bolts that hold the battery down was rubbing a tiny hole in a wire and shorting it out. You could hardly tell it's there. After thousands of dollars in parts, repairs, and towing bills, I fixed the problem with 4 cents worth of electrical tape and wire loom. I guess it finally rubbed a hole big enough in the harness wrap where I could see it. I'm going to loosen the battery up today and move everything over so it's not rubbing on anything.



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post #14 of 14 Old 02-18-2012, 10:18 AM
Jerry Bransford
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That must be why the factory installed a protective vinyl tip cover on that particular bolt. Glad you found the problem, congrats on finding it on your own... especially since the dealership couldn't even find it!!

When you have a choice, buy American made.

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