Car Tech forum: The Famous Jeep Grand Cherokee Electrical Problem

I've posted before, but here's an update: after 6 months and almost $3000 in repairs, i think, I THINK, that the problems might be resolved: problems like everyone else, cluster panel bouncing around, windows and door locks not working, engine dying, AND ALWAYS, the key entry light ALWAYS ON. It ending with replacement of the PCM. My dealer was stuck and kept on dianosing and testing the system. A LOT of contacts with Chrysler mechanics by the dealer. My dealer and mechanics were SUPER! I've still got my fingers crossed. After reading all the postings here for help (which I ran off and gave to my dealer) here's what I think: There is not a cut and dried solution to a straight problem. AND I don't think Chrysler really gives a flip or they even know. We've got a product that should be recalled every year. It may be in the hugh electric harness of wiring. Probably, this should be replaced at Chrysler's expense (it will never happen). So, this will be my last Jeep. I think Jeep was good until Ioaccoca left and Chrysler took over production. Sorry for the negativity, but folks, we spend a lot of money to have to spend this much for a mysterious problem and resolution is a ???? at that. Good luck to the rest of you. Thanks for posting and comments. They sure helped us.

This was posted on http://www.allpar.com/fix/gauges.html; it relates to the the same problems (dead gauges, etc) on a Plymouth minivan, but it sounds like his issue ultimately was with the BCM.

My wife's 92 Plymouth Voyager minivan instrument cluster went on the blink. Every gauge in the instrument cluster was dead with the "check gauges" light on. This means no speedometer, odometer, fuel gauge, etc., almost like driving with blinders on.
The factory service manual states the mechanical instrument cluster is electronic with analog display gauges. All messages to the instrument cluster gauges are sent over the "CCD" bus from the body computer. The CCD bus is a two wire differential communication bus which allows the micro-processor in the body computer to communicate with the instrument cluster microprocessor.
I called the local Plymouth/Chrysler dealer and they said they would fix it (for a small fee $$). After questioning them on what they do to fix it the service rep broke down and said it goes to an outside specialty repair service company that just fixes onboard auto electronics. He was nice enough to give me their name and phone number, and said I could go direct to them for the repair of my instrument cluster.
Ray Parker wrote: Hey, I just fixed my 89 year old mother's 1992 Dodge Caravan by following your instructions. I replaced only the Q110 transistor as all her gauges were dead, and put the body computer back in and voila, it worked again, thus saving her a bucket of money. Thanks.
I called this specialty repair company and told them my problem with the nonfunctional instrument cluster. They said they would be glad to fix it for $229 plus $58 removal/installation. I asked to speak to a tech to help me diagnose the problem over the phone to be sure this was the problem. A tech came on the phone and after telling him about my instrument cluster failure he said the problem is not in the cluster electronics but with the body computer! They have repaired over 1,000 of these body computers and it has fixed the instrument cluster problem only by replacing it with a later model body computer. The tech asked me to check the part number on the body computer to see if it was a 4686058 (it was). This part number was known to fail and the fix is to replace it with a new model 4741423 body computer.
Since I figure I was out $300 I decided to pulled the body computer module and check the PC board out myself. The body computer is under the steering column cover just to the right of the steering column in a sheet metal box with two large connectors. Once the cover is off it removes very easily with just two screws, but you should pull two connectors cabled to the body computer first. The body computer sheet metal cover has one screw (star type) attaching it. I removed this metal cover and popped out the pc board. It is a typical high volume low cost circuit board with a Motorola microprocessor and lots of discrete parts (capacitors, resistors, transistors). I took out my trusty digital volt/ohm meter and after a few minutes found two bad transistors, Q105 and Q110. The transistors were both found to have open base-emitter junctions. Without a schematic, I could trace one transistor to the chime transducer and the other to what appeared to be a bias for the "CCD" bus. Both were marked with factory numbers but I could deduce that the were "NPN" type transistors in a plastic TO-92 package. I called my brother, an EE who has an electronic lab in his home, and ask him to recommend a substitute part. He said he has a drawer full of 2N3904 (which you could pick up at a local Radio Shack for less than a buck) and to come over and get a couple. After carefully unsoldering the defective parts and soldering in the new transitors it would be a matter of minutes to check it out. I reinstalled the body computer and upon inserting the key into the ignition with the driver side door open I heard the familiar "key-in-ignition" chime again!! Good so far!
Now I started the engine and all the instrument cluster gauges came alive again!! Success!!! My brother figured the original transistors were from a bad batch and were doomed to a short life (about 4 years I guess).
I don't recommend this repair approach for everyone, but with some electronic knowledge you should be able to do this body computer repair yourself saving hundreds of dollars.

Thanks to all you guys for your help and info. Unfortuneatly I have tried most things suggested and the problems still persist.I have checked for loose connections,screws that are too long or anything that appears loose.The sentry key light [thats the one with a picture of a key with a line through it] has started coming on while driving.sometimes the car starts and runs fine then other times the engine cranks over but wont fire at all.When this occurs the sentry key light stays on and the fuel guage goes off the end of the scale past empty.The problem is much worse during wet weather which makes me think it must be a bad connection that is getting damp in it.The car sits outside at night and if it is damp in the morning wont start until the sun has been on it for a while!
I have borrowed a factory manual from my local garage which has helped to identify the various modules but is impossible to troubleshoot them without the diagnostic equipment to plug in.
It would appear to me that Chrysler have built an over complicated electrical system into their cars which coupled with a lack of build quality is causing all these problems.What happened to the good old days when JEEP stood for Just Enough Essential Parts?
I will carry on trying to get to the bottom of this and post any relevant info.
Regards Julian.

Check very carefully the battery cables and ground connections. I think if you disconnect the cable from the fuse block to the positive battery post, and put and Ohm meter on it, you will find excessive resitance due to corrosion inside the cable. I was able to eliminate many odd problems like you are describing by replacing this heavy gauge cable and the connectors. Unfortunately the dealer would have to replace the entire electrical harness which is over $300.00.

I have a 2001 Grand Cherokee 4.7L with 83k miles. Never had an electrical issue. I brought it to local mechanic because the check engine light was on. The mechanic hooked up his diagnostic machine to the cars computer and said it needed an o2 sensor. When he disconnected the diagnostic machine I lost the power windows, automatic headlights, interior lights, and overhead display that shows temperature gas mileage and distance to empty. I informed the mechanic and he said when he replaces the o2 sensor he would look into it. He checked the fuses, found no problems and said it was just a coincidence that it happened when he plugged in the diagnostic device and he couldn't help me. Luckily I found this forum and read a post that said to disconnect the battery for 10 minutes and that the computer would reset itself. I disconnected the battery and crossed my fingers and it worked. Thanks to the post everything is working properly again.

I had the same problem with mine . What worked for me was to disable the security on the jeep. Behind the glove box. The black box in the middle. I disconnected it and it runs fine for me.

This was posted by fdny136 under "Jeep Electrical". This is in the same area as the glove box, you might try it as well.


(by fdny136 - 3/23/10 7:23 PM In reply to: RE: by nomorejeeps)
I have recently repaired,after numerous hours diagnoising the bus line a 2000 grand cherokee with the symtoms described.this vehicle came to me after having a new battery,cam and crank sensor,ecm and bcm.the problem with this vehicle was on under the passenger kick panel.here you will find 2 wire harness junctions the upper harness was water damaged and corroded the solution was to use electrical contact spray and clean well,dry and treat with dielectric grease.this solved all the electrical gremlins described on this particular jeep

This is a similar problem to mine.

I have narrowed it down to the radiator cooling fans which seem to switch on and off every 12-15 seconds even when the ambient temperature is well below 0C which seems very strange...?

Do your fans do this...?

I have a 99 Jeep GC Limited, 109k mi 4.7 v8 and i'm having an issue with my battery draining quickly. Here is where my saga begins..

In september of 09 i replaced my battery, as i had not driven my jeep for about 4 months (away for work) and it was completely dead, and would not take a charge. My fault i assumed. when i tried to install the new battery i couldn't get it out because the terminals were so badly corroded, so pep boys did it for me. About a month later, the brand new battery was dead, but the terminals were solid and clean. I jumped it and it ran fine for about a week. Then it was dead again. (overnight) I took the battery off charged it overnight for a full charge, put it back in and jeep fired up no problem. i let it run for a while then shut it down. About 30minutes later i came out to drive it, and it was completely dead. This is where i am now. My battery will go from a full charge to completely dead in under an hour.

Here is what i have tried:

checked fuses (all good)
Checked connections (all the major electrical connections under hood and visable, all seem to be fine and clean)
New batteries (also drain quickly)
Used a load tester to find the draw, and tried to isolate the source, by removing fuses.

Here are more details which may be helpful.

The draw is just under 12volts, and constant.
The farthest i could trace it was behind my fuse panel (interior driverside) to one of two wires one is violet and i do not recall the other.
There is a black box/fuse?/relay? that the violet wire runs to, which makes a clicking noise when power is given.

Hopefully this makes sense to someone, and there is some sort of cheap solution. Please forgive my lack of technical knowledge. Thanks.


~Evan

can the BCM be replaced with one from another vehicle without any programming

Thanks for the response. I'll give the wires running from the door to the interior a look-see.

As far as disconnecting the battery for a period exceeding 10 minutes, then reconnecting, as expected, that provides a temporary fix. My gauges work for 7 to 10 days, then revert back to not working.

Had my 2000 JGC in a local shop for 7 full days. They have a good Jeep man, as well as people that are capable in fixing electronic problems. They went as far as replacing the instrument cluster, but nothing resolved the original problem. They have recommended another mechanic with years of Jeep experience, and I have yet to speak with him. What I wouldn't ever do, it take the vehicle to a dealer. I'd rather drive it than let those hacks overcharge me without a fix.

Skip:

Thank you for the post. I would be interested to know if this resolution provides a permanent fix for the problem. I'd (as I'm sure others would) appreciate a future update.

For those of you that think that the malfunctioning gauges may be caused by a short-circuited wire, chew on this:
- I can disconnect the battery for several hours, then reconnect, and the electrical system/instrument cluster will function fine for 7 to 10 days, before reverting back to not working. Seems to me that this indicates more than a short in the electrical system...
- The issue of the gauges not working seems to be made worse by the weather, including the cold. I noticed the gauges not working in my 2000 JGC after leaving it parked outside without being driven, for 15 days last fall. Never had an electrical problem before that.

I've also thoroughly cleaned the battery terminals. Initially, I thought that it made a difference, but in reality, it essentially "reset" the electrical system for a short period of time. After anywhere from a few hours to a few days, the gauges started acting up again.

Logically, there must be an issue occurring under the hood to cause this problem. It would be nice to find a qualified Jeep mechanic that has some experience with this issue.

As I have previously posted, my 2000 Jeep GC has had all of the issues with gauges, instrument cluster, windows, etc. I have not had as much luck with disconnecting the battery as others. It worked a couple of times but now it seems to go right back to weirding out. One thing I notice, if I unlock the doors with the passenger side door locks will driving, the gauges will come on temporarily (long enough to get a speed on my speedometer and get the windows to work) but then it will go right back to same problem. If I do this too many times it causes the some kind of cut off with my power window fuse and then I have to go under the hood to the fuse panel and pull out my 50amp fuse for the power windows and it resets the windows so that they work. Quite a hassle, you would think Jeep would work to get this problem resolved after all these years and with so many vehicles. I did talk to a friend that owns a Jeep and he told me that the transponder in the key can go bad and I need to get a new key with transponder and have the system reprogrammed. I have not tried that option yet. I do only have one key and it is possible that I have worn it out. I have 170K miles on my Jeep and this issue started at about 165K miles. I purchased the car used at 83K miles. Has anyone tried getting a new key to see if it resolves the problem with the key sentry light. Keep me posted, it is great to hear all of the feedback maybe one day Jeep will resolve the issue.

As I stated in one of my previous posts, my lock/unlock fob quit working before all of this other mess with my electical system started up. I changed out the battery in the fob and still nothing. After playing around with fuses and connecting/disconnecting the battery for the past few months, all of a sudden my fob works again and I can lock and unlock my Jeep again with it. Maybe if we keep posting enough symptoms somoeone will see a pattern which might result in a fix. Wishful thinking?

I've been watching a number of internet boards since October of last year for a resolution. Nothing has been brought to light in terms of a fix. Should you take it to a dealer, be prepared to pay $$$$$; their mechanics won't have a clue, but will start with changing out the PCM and BCM for heavy dollars. You'll get a few days out of the Jeep before the problem returns. What will the dealer say? Sorry, Charlie...bring the vehicle back, and we'll keep working on it as long as you pay us.

If the have the means, the best thing that I can offer in terms of the most cost effective solution is to trade the vehicle in on a new car. Put the thousands that you might spend on repairs toward another vehicle, and put the issues with the Jeep behind you.

The moral of this story is...DON'T EVER PURCHASE ANOTHER DAIMLER CHRYSLER PRODUCT. We expect problems with 10 year old vehicles, and we'll put up with them as long as they can be fixed. THERE DOESN'T APPEAR TO BE A FIX FOR THIS ISSUE!!!