The Famous Grand Cherokee Electrical Problem

[trevtaylor]

It seems no one has solved this puzzle yet, but I'll give it a shot of my own. Any thoughts will be greatly appreciated.

'97 Grand Cherokee Laredo, 135,000 miles

Various warning lights
Power comes on at night
Instrument cluster & gages haywire
Stalling
Dead battery overnight
Feedback in speakers
Repeatedly blown 20A fuse on engine fuse block (Automatic Shutdown Relay fuse)
Turns over, but now won't catch

Replaced: Ignition switch & ignition cylinder block, cam sensor, throttle position sensor. Cost: $750

Tried: new battery, unplugging PCM computer, checked all fuses.

And the alternator checked out all right. (according to the dealer)

Any ideas?...the dealer in stumped. (replacing the PCM computer seems to only have a 50% success rate, although they are avail. on e-bay for $249 w/ a 12-month warranty)

 

[pinaplebob]

I don't have a GC but on my Xj, I had a bunch of weird electrical problems and warning lights. Found my computer which was mounted on the fender had worn through the wires between it and the fender. They were curled underneith the computer and then it was bolted down. It was a pain but after a ton of splices, everythings all good for the time being. Like I don't know if it is the same with you, but it's worth checking.

 

[TwistedCU]

It seems no one has solved this puzzle yet, but I'll give it a shot of my own. Any thoughts will be greatly appreciated.

'97 Grand Cherokee Laredo, 135,000 miles

Various warning lights
Power comes on at night
Instrument cluster & gages haywire
Stalling
Dead battery overnight
Feedback in speakers
Repeatedly blown 20A fuse on engine fuse block (Automatic Shutdown Relay fuse)
Turns over, but now won't catch

Replaced: Ignition switch & ignition cylinder block, cam sensor, throttle position sensor. Cost: $750

Tried: new battery, unplugging PCM computer, checked all fuses.

And the alternator checked out all right. (according to the dealer)

Any ideas?...the dealer in stumped. (replacing the PCM computer seems to only have a 50% success rate, although they are avail. on e-bay for $249 w/ a 12-month warranty)

Too many things on separate electrical circuits are affected to be a common problem - unless it is the PCM, which is what my money is on.

 

[97_Cherokee]

Check all the ground cables, I've heard of them snapping inside the protective coverings (newer sierra's and silverados), rusting out, or just loosening. Faulty grounds can cause some serious issues, causing many of the symptoms you describe. Many times a faulty pcm is a diagnosis for symptoms caused by faulty grounds.

 

[trevtaylor]

'97 Grand Cherokee Laredo, 135k, 6cl., 4.0 (2 outta 4 speakers totally jamming)

Please see my previous post for symptoms, several fixes and about a dozen things to check for yourself.

What finally solved it:

PCM Computer - replaced it.
Oxygen Sensors - replaced them both.

PCM (also called ECU or ECM), bought rebuilt off E-bay from a FL co. 275.00 with shipping and a 12 month warranty (6 mo's pro-rated). It wasn't good-looking, a little corrosion & weakly spray-painted, but works so far.

O2 sensors, bought for 49.99 each from oxygensensors.com. Walker brand. The website shows pics of damage. Mine pretty much had it all: lead, anti-freeze, silicone & rich-fuel mixture contamination. Apparently, O2 sensors send a ton of info to the computer. My engine has never sounded better. Should replace them anyway after 50-80,000k. Also, suppossed to save you about $60 a year in gas.

Anyway, she came back from the dead and started. Gages were haywire & engine stalling/reving were tempermental for a few minutes, and it seemed like it wasn't fixed, but everything settled into the norm. I am guessing here, but my interpretation was that once the computer talked to everything...she set the correct parameters. However, it's only been one day so far and it does seem to still have a .000001% recurrance. I'm under the impression that it'll settle down.

If my problems return, I will return to the board and post. That's the thing I'd like to ask of everyone: if you use the board...post your final fix. Dealers across the country are stumped by this problem.

Otherwise, all this is gone:
stalling, battery drain, 20a mini-fuse repeatedly blown, gages haywire, warning lights, alarm haywire, power on at night.

Finally, I'd like to thank everyone who has posted and continues to help folks. It is quite endearing and appropriately warm-spirited for the '08 Holiday Season.

 

[97_Cherokee]

Glad you fixed the problem. I replaced my O2 sensors this year in my truck with 256000kms on it for the first time and didn't notice a difference but in your case I think if your seeing damage like that on your sensors, replacing them is only a band-aid solution. The rich-lean problem I could see from the bad PCM but coolant? Sound like a head gasket or another problem.

 

[trevtaylor]

i humbly return after my original post to sadly report that most of the problems are back. so, it wasn't the PCM, it's not the Power Distribution Center (i completely took it apart to check for corrosion), and i'm now back to square one, having read all the tech bulletins on alldata. they officially call it a IOD or Ignition Off-Draw. which starts with the air bag warning light and leads to basically all electrical going haywire and ends with stalling & no-start. so, if it's not the PCM, and there are thousands of cases of this reported around the country, then it must be something common, right? a shorted wire or bad ground wouldn't be common. it has to be something like...the radio running too hot or the junction box being kicked every time a passenger gets inside. any thoughts? i'm off to check for an internally-shorted generator.

 

[idrthrbfishing]

I don't know if you tried this yet, it may sound so simple it was overlooked, it may not even be the cause... but I had a 97 tj with dash board errors and hard starts. stalling on a good jar from a bump. I talked to a jeep salesman I know he told me to check all the connections on the back of the dashboard. I found a them loose I removed and reset them all. after which I had no more issues with any starting running or dash board lights going crazy. Sound like you may be having a problem a lot like mine. good luck hope it helps.

 

[Low Ranger]

Do you have a tow bar? I have a ZJ and after playing in a mudhole things started going haywire. What I had was corrosion in the trailer light plug. Shorted everything toghether. Check it you haven't.

 

[CobraBlu79]

I had same issues with my 2000 Jeep Grand Cherokee Laredo (92,300 miles). Replaced battery - did not fix the gauges from spinning, lights, radio, fan etc from not working. Took car to mechanic who scanned it and it pointed problem toward the BCM or PCM for a cost of $1,200+. He tried one more step before going this route and found an electrical short under the center console cover near the shifter. So many components were grounded to this one spot. He fixed it and it's been perfect since. Cost - $150 for 2+ days of troubleshooting. For those who still have the issue I would try looking at this spot as he found it thru some research thru Jeep technical bulletins.

 

[Simtech]

Ok, I'll try to make a long story short but I had this issue with my '01 JGC. Dash lighting, windows, locks all stopped working but it would start and run ok....for a while. Then it wouldn't even start. With nothing done to correct it, the jeep would start running again just fine a couple of days later. Then it would start the whole cycle over again, and again. So I decided to look at it myself. I found another thread with some detailed information about tracking PCM signals and specific voltages (see 2001 Jeep Grand Cherokee: 6 cyl 4.0 liter..PCM. Ultimately I ended up disconnecting every module attached to the pcm bus, and there were a lot of them. One of them must have been a bad connection that was loading the bus down because that was over a year ago and I have had no problems since. There are many different modules in many different places so this took a couple of days to complete but was worth it in the end.

 

[Campbell80]

I'm having problems with mine not turning over but when I wiggle the gear the gear shift it starts right up. I've changed the neutral safety switch, throttle position sensor, cleaned the coil packs, checked the battery terminals. Do you think I should change the Starter Relay next or what? I'm at a loss!