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Unread 09-04-2013, 08:41 PM   #1
01zerone
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Wj WJ electrical issues (BCM/PCM/AirBag/ABS/etc...)

I've read miles and miles of various information on this forum for my 2000 WJ electrical issues, tried just about everything there was to try to fix it, but still no solution. However, today I came across something interesting I thought I'd share with you guys, and maybe together we can solve this once and for all! So if you're fed up with "the gremlin", and ready to either get rid of your ride or hang yourself, don't do it just yet

Problem description:
Intermittently, my AirBag light comes on, accompanied with the lovely chime and the Check Engine light as I drive down the road. Then it goes away for a bit, then it comes on again, then off again... Sometimes, when I start the car in the morning, the instrument cluster gauges are dead and all the warning lights are ON, and power windows don't work. Then, of course, after driving it for a while, it goes away by itself. On the dash I get error codes P1687, P1686, P1685.

What I've tried so far:
- replaced BCM
- replaced battery, cleaned terminals
- checked wiring for obvious cuts/burns/etc - all looks nice and clean
- checked and cleaned just about every connector I could find
- sacrificed a goat to the WJ god
no fix

Now, the interesting part:
As I was going through the connectors, underneath the steering column I found, what turned out to be a PCI bus diagnostics port, which looks like this:





This is the place where all the PCI bus wires come in together. The plastic cap that connects to it, is actually a "terminator", that connects all the wires to each other. If you unplug that and start your car, you'll see all the symptoms you've probably been seeing, and more.

So, what I'm thinking is one of them is causing all the problems. It sends a bad signal, a noise, an incorrect voltage to the system, and the rest of the modules pick it up and replicate (since they are all interconnected), thus displaying weird symptoms (in my case, instrument cluster going wild and windows not working), which may not actually be the problem in the first place.

If you're having same issues, let's try this together, see if there's a logic to my conclusion: what I've done is disconnected the AirBag bus wire from this port (since it's my first suspect on the list) to isolate the problem. So far, only the AirBag light is on, I haven't seen any other issues (knock on the wood). I'm going to drive it like that for a few days and see what happens. If nothing else comes on, then I'll know it's the AirBag module that throws out noise on the bus, causing other modules to act crazy.

BTW, here's wiring color-coding:

all wires are YELLOW + PURPLE +
RED - instrument cluster
WHITE - BCM
BROWN - SKIM/ABS
GREY - PCM/TCM
ORANGE - AIRBAG
BLUE - (I've no idea)

Does this sound logical to you? Anyone with 2 cents, please reply! If we solve this, we no longer have to shoot in the dark, replacing various modules hoping to find that one bad apple.

image-1-.jpeg

image.jpeg

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Unread 09-04-2013, 08:46 PM   #2
StormChaserTim
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Fascinating.

Just a quick question, though. Could it be that the terminator itself is causing the issue? Perhaps some oxidation on a pin or something causing a resistance issue that may create this problem?

Tim
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Unread 09-04-2013, 09:45 PM   #3
losttech
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OK I had a very similar issue here is something to try.
Start your jeep and turn the steering back and forth fairly fast if you get the airbag light and check engine thing to go on and off while doing this its your clock spring in the steering column.

It will be very obvious if its related as soon as you move the steering wheel back and forth the airbag light will kick in and chimes and lights will start going off.

thats the only help I can offer if it is the clock spring not a hard or expensive fix.
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Unread 09-05-2013, 04:14 PM   #4
rdkendrick
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Quote:
Originally Posted by losttech View Post
OK I had a very similar issue here is something to try.
Start your jeep and turn the steering back and forth fairly fast if you get the airbag light and check engine thing to go on and off while doing this its your clock spring in the steering column.

It will be very obvious if its related as soon as you move the steering wheel back and forth the airbag light will kick in and chimes and lights will start going off.

thats the only help I can offer if it is the clock spring not a hard or expensive fix.
If your cruise and radio buttons work, it's likely that your lock spring is okay, and the problem is your ACM.

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Unread 09-05-2013, 05:00 PM   #5
01zerone
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first, quick replies:

Tim - highly unlikely, but of course never hurts to check/clean. that terminator is simply a copper connector that connects all those pins together. my idea was to disconnect one wire at a time for a day or two, until everything runs well with no errors. process of elimination.

losttech - i forgot to mention that i've already took apart the steering wheel airbag and cleaned the clock spring and all the connector. that's not it.

now, the update:
so i ran a day with the AirBag wire disconnected, but in the morning the symptoms were back. now connected that wire back in and disconnected the YELLOW+PURPLE+BLACK (i don't know where it goes to), but i ran about 80 miles like that today and no issues, no lights, nothing so far. i'll see how it behaves in the morning.

in fact, today i found an article that's very similar to what i'm proposing to do, it just goes into details of the PCI bus voltage and how to test, but the core idea is the same - find the bad signal source that causes all these weird symptoms, throwing everyone off when trying to troubleshoot.

http://www.autofixlist.com/main.do?a...ID=4&menuID=58
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Unread 09-16-2013, 08:23 PM   #6
01zerone
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final update: my gremlin is GONE! melted wire.

as per my initial thread, it helped me to narrow down the problem going though PCI bus one by one. in my case, the one that didn't make the AirBag come on (my initial symptom), was the BCM wire. i started chasing the wires that were applicable to the BCM (lights, doors, etc...) and found the melted wire.

in conclusion, when you have electrical problems as described above, follow below steps that i've gathered around the internet, as well as some observations of my own:
- error messages on the dash may be misleading. i had AirBag light on, and turned out the problem had nothing to do with my airbag system
- start with the basics: clean the battery terminals, make sure your battery is good. if it's draining, test for the "parasitic draw". good link:
- clean as many connectors as you can find. look for corrosion. if your pins look corroded, there's a good chance you'll find the problem there
- in short, most likely it's your wiring. this is where you should start (besides, it's the cheapest route to take)
- my initial post will help you to at lest start looking in the right area. PCI bus elimination process will save you time
- DO NOT replace any of the modules until you find the problem! it is highly unlikely that the module just got burned by itself. having said that, after you find the wiring issue, drive around for a while, and if the problem persists, then you may have to replace the burnt module.
- don't believe in gremlins - they don't exist, trust me. this comes from a former believer

hope it helps. good luck!

Last edited by 01zerone; 09-17-2013 at 10:26 PM..
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Unread 09-17-2013, 10:42 AM   #7
rdkendrick
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01ZERONE

Glad you got it fixed. Good research on your part and you came back and posted the fix.
We like members who do that. Good job!

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Unread 09-17-2013, 07:37 PM   #8
01zerone
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Quote:
Originally Posted by rdkendrick View Post
01ZERONE

Glad you got it fixed. Good research on your part and you came back and posted the fix.
We like members who do that. Good job!

Sent from my iPad using my fingers
hope i can help someone like many others have helped me by taking time to post their ideas
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Unread 09-28-2013, 07:26 PM   #9
dnitz71
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I have the same type of problem with my 01 WJ. Thanks for the great info. Can you be more specific as to where the melted wire you found was. Some times problems occur in common places Thanks


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Unread 12-23-2013, 12:51 AM   #10
01zerone
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it was in the rear lights, had to replace both of them.
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Unread 12-26-2013, 10:06 AM   #11
rickdod
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This is a very interesting thread...I will for sure have to try it!

Something I noticed with my electrical issues is that when I unhook the battery and let the system reset...whenever I start the vehicle again everything will be working normal...except the Seatbelt light will ALWAYS stay on. So I'm working if my gremlin is coming from something in the seatbelt sensor wiring?

Any ideas or input?
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Unread 01-14-2014, 11:29 PM   #12
aiden8
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sorry can u pls clarify a bit more? what wire? in the tail lights you found 2 burnt? and replaced them?

im having the same issue, recently replaced bcm, cluster, tried the fuse box. Its had electrical work done to it before and definitely not close to professional. after i replaced the bcm i was doing ok with all gauges, speedomter etc for not even a day of all day driving (airbag and key light with a slash thru it would stay on).. read about terminals, mine looked like old balls so i replaced both, now are working again with same airbag/orange key symbol. havent driven it yet just on and off everyday for the past few days. any advice would be awesome blossom
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Unread 01-16-2014, 09:07 AM   #13
01zerone
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hi there,

yes, my tail light wires were causing me problems. however, every problem is different, obviously, so you have to find what caused your BCM to go out. if i were you, i'd start tracing the wiring you said looked like someone worked on them. the essence of this troubleshooting thread is to help find the wiring problem by narrowing down the problem using PCI bus elimination process. again, find the problem FIRST and only THEN replace the BCM or whichever computer. they don't just go bad for no reason.

hope this helps. good luck!



Quote:
Originally Posted by aiden8 View Post
sorry can u pls clarify a bit more? what wire? in the tail lights you found 2 burnt? and replaced them?

im having the same issue, recently replaced bcm, cluster, tried the fuse box. Its had electrical work done to it before and definitely not close to professional. after i replaced the bcm i was doing ok with all gauges, speedomter etc for not even a day of all day driving (airbag and key light with a slash thru it would stay on).. read about terminals, mine looked like old balls so i replaced both, now are working again with same airbag/orange key symbol. havent driven it yet just on and off everyday for the past few days. any advice would be awesome blossom
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Unread 01-16-2014, 09:14 AM   #14
01zerone
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sorry for the late reply... if it's just the seatbelt light, then definitely start working on the seatbelt switch. you can either test it or unplug it and manually connect the wires. basically, find out if it's actually the seatbelt wiring problem or something else, causing your BCM to put out a wrong warning.

good luck!

Quote:
Originally Posted by rickdod View Post
This is a very interesting thread...I will for sure have to try it!

Something I noticed with my electrical issues is that when I unhook the battery and let the system reset...whenever I start the vehicle again everything will be working normal...except the Seatbelt light will ALWAYS stay on. So I'm working if my gremlin is coming from something in the seatbelt sensor wiring?

Any ideas or input?
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Unread 05-25-2014, 09:34 AM   #15
ericthebrown
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sorry to resurrect an old thread, but i have a quick question. First Jeep, and of course I'm having electrical issues involving gauges, windows, locks, and a/c. Jeep in question is 2000 WJ 4.0. I noticed in the pictures the OBDII terminator. There isnt one to be found in mine and I'm wondering if it is a required item. Closer looks at the pictures show the plug connecting every wire. I'm hesitant to mark all wires and diagram where they go so I can pull them all to see what happens if link them together. Anyone know where I can find one of these terminators? Thanks in advance
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