trevtaylor
New member
1997 Grand Cherokee Laredo, 135,000 Miles
Although I'm posting/re-posting this fix, please feel free to keep adding threads so we can follow the issue all the way.
It's amazing. There must be an international invention contest where we can nominate "1996Jeep GC" (the author's handle) for an award and research grant.
Anyway, I'm gonna try it myself. Having trolled 4 other website's boards, I can say that I've seen this problem reported hundreds, perhaps 1000-2000 times and no one has ever reported a solution besides this great man. Usually, the best advice is either to fix & sell or just douse with gas & light a match. (especially for us owners of the proported "lucky" years of 1996-1998)
As I'm going to post this on multiple boards (credit given to "1996Jeep GC" on cnet.com, car tech forum. There you can see the original description and the 67 gushing & blushing replies.), in order to save people hard-earned funds - I'm going to list all the usual symptoms and lay out the repair. (sorry for the repeated information, I only feel like writing this once)
Symptoms: (these usually start with 1 or 2, then worsen to include all of these) stalling, power on at night, repeatedly dead battery, instrument cluster & gages haywire, warning lights, turns over, but won't start, blown fuse on engine block fuse box (in mine, the 20a mini-fuse, the Automatic Shutdown Relay) and to a very lessor extent, very, very slight acting-up in the stereo speakers and tiny, tiny transmission sluggishness is the only way I can think how to describe it.
The Fix: (as unbelieveable as this sounds, but reported to have almost a 90% success rate from around 45-65 people)
BACK THE SCREWS HALFWAY OUT ON YOUR PCM COMPUTER COVER.
Then try to start.
Apparently, over time, these screws are pinching something. Either the bracket inside the cover, the guts inside, or the fat PCM connectors on the outside are weighing down and pinching the pins. Or something else. Anyway, it works. (although, after time, the success rate goes down (for some people) as the problem may return...maybe down to 70%, but then messing with the PCM again jiggles this figure back up & down) Literally, hundreds of Dealers couldn't figure this out (what'd we spend?...$1200.00 each x's 5000 instances=6 million dollars. I'd say the total is much more than that) and it was up to an Aircraft Mechanic to solve this for all of us. (and I've seen posts for this problem from 1996-2006 owners for many Chrysler vehicles besides Grand Cherokees.)
The Directions: (as given from a 1996 Grand Cherokee Owner, I have a 1997) PCM Computer (located on firewall, passenger side, behind the engine coolant over-flow container). It looks like a very-large computer hard-drive. About 10" x 8". Has 3 fat hose-connectors.
Remove plastic coolant container. Back off the two screws on the PCM cover. They are about 1/2" long. Back them off half-way. Try to start and if so, take it out for a spin. Evaluate stalling & electronics. You may now have to re-check for blown fuses as the haywire PCM has been shooting out sputtering energy everywhere. As recommended, replace screws with 1/4". Some people even filed their 1/2" screws down.
Besides this miracle, here are the usual suggestions for the fix from 5 different auto website forums: most popular: (1) new alternator as they often, often check out fine and amps can still be low (volts appear normal) from the internal regulator and bad diodes will cause a drain. (2) Replacing the PCM (about a 50% success rate). Dealer cost: $1000.00, Ebay: remanufactured with a 12-month warranty (programmed to your VIN) $249.00 (make sure you check their customer ratings). (Also, it's been recommended to unhook the battery before uninstalling or installing PCM, I guess so there's no surge into the PCM or some other reason). (3) Replacing the Ignition Switch & Ignition Cylinder Lock as these codes often come up on diagnosis (cost=$275.00). And (4) replacing the Cam Sensor & Throttle Position Sensor (cost=$450.00)
The rest of the suggestions:
A) In your engine fuse block, mark first, then pull out all fuses and scrub them with scotch-brite and contact cleaner. All relays & contacts. (this has been reported to work for many, many folks as the problem (which will spout out dozens & dozens of symptoms) appears to have been cornered between here (the engine fuses) and the PCM computer.
1) Check everywhere for melted wires.
2) Remove positive battery cable for 1 hour in order to reset PCM computer and lock/unlock door to reset key. (although 1 person told me to do this for 4 hours)
3) Check for loose cable on PCM. (and wiggle them while running to see if it starts to stall)
4) Check for frayed wires in door frame, crimping is common. Tighten door hinges.
5) Repeatedly blown fluses is typical of frayed wires.
6) Confirm rear-window wiper is housed and not stuck in idle position.
7) Inspect wires under driver floor mat. Wetness is common under carpet.
8) Check for feedback in speakers.
9) Try unplugging 5 fuses at a time (from engine fuse block) and try to determine which one is draining battery overnight.
10) Confirm fuel pump is clicking when in ACC before actually trying to start.
11) When starting try hitting various other power switches, like rear-window wiper. (this worked for some people)
12) Unplug/replug wires to distributor.
13) Confirm clean battery terminals/cables. Inspect all 3 grounds to Alt., Batt., & block. (this's also a very, very popular suggestion and indeed finding loose grounds worked for several folks)
14) Check all fuses in both fuse blocks. Especially the AUX and ECU (although I never found mine. Is the ECU the PCM?). Replacement may blow again (immediatedly) or in 5 minutes to 3 days.
16) When instrument cluster & gages go haywire, this's indicative of a charging problem. Replacing the cluster does not solve problem.
17) Replacing Voltage Conjuntion Block does not work.
18) Check hood bulb and other bulbs and confirm they meet Jeep specs.
19) Unhook PCM and rehook to check starting.
20) Check for circuit boards burning up.
21) Replacing oxygen sensors.
22) There's also a lot of talk about weird happenings with power windows & the alarm. Apparently, each model & year may be different, but reported many times is that the alarm cannot be unhooked. It's hard-wired into the system. Again, I believe the idea that's being forwarded is that whatever your weird symptom, it's been tracked down to the PCM and the fuses inside the engine fuse box)
22) And basically every other idea that is however remotely connected to the random symptoms that plague all of us differently.
Again, thank you to "1996Jeep GC" on Cnet's Car Tech Forum. He's the author of the most-successful fix. An actual hero in many peoples' minds. Also, thank you to everyone who offered the above-mentioned fixes. And thank you for all of the future suggestions. Hopefully the mediators who watch these boards will do whatever they do in order to keep this fix available to all members & guests. As I resolve my own problem, I will update & post as I hope you will also.
Although I'm posting/re-posting this fix, please feel free to keep adding threads so we can follow the issue all the way.
It's amazing. There must be an international invention contest where we can nominate "1996Jeep GC" (the author's handle) for an award and research grant.
Anyway, I'm gonna try it myself. Having trolled 4 other website's boards, I can say that I've seen this problem reported hundreds, perhaps 1000-2000 times and no one has ever reported a solution besides this great man. Usually, the best advice is either to fix & sell or just douse with gas & light a match. (especially for us owners of the proported "lucky" years of 1996-1998)
As I'm going to post this on multiple boards (credit given to "1996Jeep GC" on cnet.com, car tech forum. There you can see the original description and the 67 gushing & blushing replies.), in order to save people hard-earned funds - I'm going to list all the usual symptoms and lay out the repair. (sorry for the repeated information, I only feel like writing this once)
Symptoms: (these usually start with 1 or 2, then worsen to include all of these) stalling, power on at night, repeatedly dead battery, instrument cluster & gages haywire, warning lights, turns over, but won't start, blown fuse on engine block fuse box (in mine, the 20a mini-fuse, the Automatic Shutdown Relay) and to a very lessor extent, very, very slight acting-up in the stereo speakers and tiny, tiny transmission sluggishness is the only way I can think how to describe it.
The Fix: (as unbelieveable as this sounds, but reported to have almost a 90% success rate from around 45-65 people)
BACK THE SCREWS HALFWAY OUT ON YOUR PCM COMPUTER COVER.
Then try to start.
Apparently, over time, these screws are pinching something. Either the bracket inside the cover, the guts inside, or the fat PCM connectors on the outside are weighing down and pinching the pins. Or something else. Anyway, it works. (although, after time, the success rate goes down (for some people) as the problem may return...maybe down to 70%, but then messing with the PCM again jiggles this figure back up & down) Literally, hundreds of Dealers couldn't figure this out (what'd we spend?...$1200.00 each x's 5000 instances=6 million dollars. I'd say the total is much more than that) and it was up to an Aircraft Mechanic to solve this for all of us. (and I've seen posts for this problem from 1996-2006 owners for many Chrysler vehicles besides Grand Cherokees.)
The Directions: (as given from a 1996 Grand Cherokee Owner, I have a 1997) PCM Computer (located on firewall, passenger side, behind the engine coolant over-flow container). It looks like a very-large computer hard-drive. About 10" x 8". Has 3 fat hose-connectors.
Remove plastic coolant container. Back off the two screws on the PCM cover. They are about 1/2" long. Back them off half-way. Try to start and if so, take it out for a spin. Evaluate stalling & electronics. You may now have to re-check for blown fuses as the haywire PCM has been shooting out sputtering energy everywhere. As recommended, replace screws with 1/4". Some people even filed their 1/2" screws down.
Besides this miracle, here are the usual suggestions for the fix from 5 different auto website forums: most popular: (1) new alternator as they often, often check out fine and amps can still be low (volts appear normal) from the internal regulator and bad diodes will cause a drain. (2) Replacing the PCM (about a 50% success rate). Dealer cost: $1000.00, Ebay: remanufactured with a 12-month warranty (programmed to your VIN) $249.00 (make sure you check their customer ratings). (Also, it's been recommended to unhook the battery before uninstalling or installing PCM, I guess so there's no surge into the PCM or some other reason). (3) Replacing the Ignition Switch & Ignition Cylinder Lock as these codes often come up on diagnosis (cost=$275.00). And (4) replacing the Cam Sensor & Throttle Position Sensor (cost=$450.00)
The rest of the suggestions:
A) In your engine fuse block, mark first, then pull out all fuses and scrub them with scotch-brite and contact cleaner. All relays & contacts. (this has been reported to work for many, many folks as the problem (which will spout out dozens & dozens of symptoms) appears to have been cornered between here (the engine fuses) and the PCM computer.
1) Check everywhere for melted wires.
2) Remove positive battery cable for 1 hour in order to reset PCM computer and lock/unlock door to reset key. (although 1 person told me to do this for 4 hours)
3) Check for loose cable on PCM. (and wiggle them while running to see if it starts to stall)
4) Check for frayed wires in door frame, crimping is common. Tighten door hinges.
5) Repeatedly blown fluses is typical of frayed wires.
6) Confirm rear-window wiper is housed and not stuck in idle position.
7) Inspect wires under driver floor mat. Wetness is common under carpet.
8) Check for feedback in speakers.
9) Try unplugging 5 fuses at a time (from engine fuse block) and try to determine which one is draining battery overnight.
10) Confirm fuel pump is clicking when in ACC before actually trying to start.
11) When starting try hitting various other power switches, like rear-window wiper. (this worked for some people)
12) Unplug/replug wires to distributor.
13) Confirm clean battery terminals/cables. Inspect all 3 grounds to Alt., Batt., & block. (this's also a very, very popular suggestion and indeed finding loose grounds worked for several folks)
14) Check all fuses in both fuse blocks. Especially the AUX and ECU (although I never found mine. Is the ECU the PCM?). Replacement may blow again (immediatedly) or in 5 minutes to 3 days.
16) When instrument cluster & gages go haywire, this's indicative of a charging problem. Replacing the cluster does not solve problem.
17) Replacing Voltage Conjuntion Block does not work.
18) Check hood bulb and other bulbs and confirm they meet Jeep specs.
19) Unhook PCM and rehook to check starting.
20) Check for circuit boards burning up.
21) Replacing oxygen sensors.
22) There's also a lot of talk about weird happenings with power windows & the alarm. Apparently, each model & year may be different, but reported many times is that the alarm cannot be unhooked. It's hard-wired into the system. Again, I believe the idea that's being forwarded is that whatever your weird symptom, it's been tracked down to the PCM and the fuses inside the engine fuse box)
22) And basically every other idea that is however remotely connected to the random symptoms that plague all of us differently.
Again, thank you to "1996Jeep GC" on Cnet's Car Tech Forum. He's the author of the most-successful fix. An actual hero in many peoples' minds. Also, thank you to everyone who offered the above-mentioned fixes. And thank you for all of the future suggestions. Hopefully the mediators who watch these boards will do whatever they do in order to keep this fix available to all members & guests. As I resolve my own problem, I will update & post as I hope you will also.
