WJ Electrical Problems with Instrument Cluster, Windows, Heater, EVIC, Alarm and more - JeepForum.com
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post #1 of 7 Old 04-12-2010, 07:06 PM Thread Starter
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WJ Electrical Problems with Instrument Cluster, Windows, Heater, EVIC, Alarm and more

Hi Folks,
I'm new to this forum and to Jeeps. I bought a yr 2000 WJ Grand Cherokee Limited, 4.7 V8 3 weeks ago with a known electrical fault. I'm now feeling like I've bitten off more than I can chew...It was a really good deal!

The engine starts and stops perfectly, all my problems occur within the cabin.
While the engine is running, about half a dozen warning lights appear on the dash cluster, all the gauges drop to zero, the electric windows stop working, the alarm can be armed but activates when you unlock (and open) any of the doors. The heater blower works but the cabin temperature cannot be varied. The heated seat lights come on (on the switches) but the seat elements don't heat. The steering wheel mounted radio controls don't work. The overhead computer display doesn't update its display for milage/mpg/temp (apart from the compass) and the rear window/mirror defrost doesn't work.

What I have noticed though is that the majority of these problems disappear with the engine off and the ignition in the On position. In the Ignition On position, the PCI bus voltage reads normal (0 to 2.5V). With the battery disconnected the PCI bus resistance is 350 Ohms. Disconnecting modules and measuring bus continuity throughout the circuit doesn't show any breaks (resistance is no more than 0.2 Ohms).

With the engine running, PCI voltage creeps up to 7.3V (today however it showed 0V !!). This can be temporarily solved by disconnecting the negative terminal from the battery for 10mins+.

I've tried disconnecting modules and waiting for the voltage to drop, the bus still reads high voltage, the only modules I haven't tried yet are the airbag, PCM and zone control modules (so I might answer my own question soon!).

I can't help thinking that the difference between ignition On and Run (engine running) is the main issue..but I can't see how best to troubleshoot it.

My next checks are the PCI voltage with the airbag and zone control modules disconnected to rule them out.
Also the cigar lighter doesn't work and the passenger door lock motor seems to stick closed. I don't know if these two problems will have anything to do with my main problems but I'm clutching at straws, hoping that ruling them out will help me find the main issue.

The battery reads 12.5V static and 14 running, the terminals make good contact with earth and the fusebox live. I don't have any stalling issues and the engine starts really easily. All the external electrics work well, eg. lights, wipers, indicators, hazards, wing mirror folding! I can't see any water damage anywhere and I've been over all the earths ensuring they're making good contact.

It really is a puzzler..and I'm hoping that somebody reading this has been down this road before, recognises the above faults and knows where I can look next. It really is a fantastic machine, absolutely perfect apart from this bit of grief. If I have to replace the PCM or BCM then i'll do it but I wanted to rule out wiring and other modules first.

Finally, with my basic scanner...I've managed to get error codes p1686 ("No SKIM Bus Message Received") and p1698 ("No CCD Messages Received From TCM") from the OBDII diagnostic port (engine running). I can't tell alot from this other than the messages on the PCI bus are being corrupted / lost. Alot of the advice I've read is to take it to let somebody with a DRBIII scan tool check the system...will that device be able to find anything more than the above error codes?

All suggestions / ideas welcome?

Thanks in advance


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post #2 of 7 Old 04-16-2010, 03:32 PM Thread Starter
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Update - I found a website that listed the resistances of each of the modules. 3300 Ohms for the PCM, 2400 Ohms for the instrument cluster and 10800 Ohms for all the others. You disconnect the battery, take the cap off the Diagnostic Junction Port and measure the resistance at each pin. Lo and Behold...All of the separate PCI circuits had the correct resistance.
This tells me that the PCI circuit is complete, and that all the modules are ok.

The only other thing I can think to do is to try the same tests but with the ignition switch at the run position...to see if there's a link to the different fused power supply.

If that yields nothing I can't think what to try next.

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post #3 of 7 Old 04-16-2010, 04:50 PM
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Each and everyone of those things runs through the BCM. (Body Control Module) I would suggest taking it down to the dealership so they can scan it with a DRB III scan tool. They will be able to tell if that is functioning properly or not. More than likely there is a bad wire between the BCM and battery.

If you dont know, the BCM is located above the fuses inside the cabin under the drivers side dash.

I had similar issues (not all of the ones you are having, but most of them) when I bought my 2000 about a year ago. Dealership charged me about $180 to scan, locate, and fix the bad wire. All was good after that.

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post #4 of 7 Old 04-18-2010, 04:44 PM Thread Starter
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Thanks ezflip..I think the dealership (or somebody with the right scantool) probably is the next step, will post back once I get a result.
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post #5 of 7 Old 04-28-2010, 06:01 AM Thread Starter
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Just to close this out...a replacement alternator fixed all my problems!
No difference to the way it charges the battery, but there must have been a fault in the old one that disrupted the modules!!!
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post #6 of 7 Old 01-26-2016, 08:35 AM
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instrument panel fixed

I have a 1997 Jeep Grand Cherokee Larado. My instrument panel was intermittently shutting down and coming back on and finally stopped working. I read on here to clean the instrument panel plug, so I did and it didn't change anything. Also when this happened my windows stopped working and my door locks would only open and not lock. When I had the key out of the ignition my door locks would work and also the wireless lock/unlock would work fine . I did the usual checking of battery voltage, alternator output, cleaned the battery and engine grounds but nothing solved the problem. I checked all the connections under the dash and still nothing worked. I read where it was my BCM or a bad relay or fuse. I checked all fuses and relays all were good. What it ended up being was a poor connection in my overhead console plug. Only reason I checked this was the overhead lights were sometimes not coming on when I opened up the door. I took the overhead console off and the plug connecting the display wasn't seated all that great so I pulled that out and replugged and everything started working again even the temperature/direction display. It only had --- for years but it turned out was a poor connection at that plug and eventually worked loose enough to not have a good ground for the other items. I hope this helps some of you.
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post #7 of 7 Old 01-26-2016, 11:21 AM
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Did you do the key dance, 3 on/off and see if you have any codes?
Did you check the wires in the door boot?
Darnice is offline  

bus , gauges , pci , voltage , windows

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