Jeep Grand Cherokee stalling fixed!

Okay, I still haven't changed the PCM. I did however buy one of those mighty-vac pumps and checked the vac circuits. The one that feeds the dash and cruise control was leaking like a sieve at the two T connections on the firewall. I fixed them with some RTV and it no longer dies while sitting idling through warm up cycle. It does however, jump like the switch is cut off while at road speed. The battery gauge drops to battery voltage and the RPM and speedo drop,(no codes) then without any intervention from me, it runs great. It only runs right when it's totally saturated with heat. I think it's in the generator or the voltage regulator circuit in the PCM. So, it looks like I've been chasing two similar, but unrelated problems. The saga continues...

Had a no starting problem with JGC'97. Turned to be a failing relay. After that got a "check engine" light and no overdrive.
Turned to be a bad transmission relay. Went to the parts store and changed the rest, they cost ten bucks a piece. Good luck to everyone.

know how u feel...this is the point where my 96-4.0 went off the cliff. 85-110k is the magic nr for Oxy sensors to start failing. I went crazy trying to exact pinpoint problem. Found a lean condition melting cat conv.-- Cause : according to mech at 5-5tar dealer, brain is losing link to ID of vehicle. in other words it's forgetting where it is. Usually vehicle won't run in this conditon but Jeeps seem to plug on anyway. remedy: reflash brain and install update. I replaced Oxy sensors (both) w/ OEM. I was also getting ckt failure codes for O2. Had already bought brain. So I warranteed it and then had it programmed to vehicle at Dealer. ended probs. previous brains were installed and not id'd to vehicle.I paid to have it done but found out that it wasn't done after all..... dealer probably the only place u find a two way scanner AND connection to web page with download codes for ID.
AS far as scanner reading codes... only hard codes are registered and readable, however scanner can give u voltages and values at most sensors in real time and freeze data from exactly when codes are set. My scanner informs me as to high or low values but this is from OBDII. You have done some good thorough research; and listed valuable info that is not easy to accumulate. I consider this important to this forum. It is my belief that there are fixes in this latest update that Chrysler isn't really admitting to. the update is a warranty/recall no charge item as far as I know...that is: It didn't cost me anyway. Installation took 30 - 45 mins. w/ several checkpoints along the way. The Mech I was dealing with told me a battery going flat on these Jeeps causes ckts to be dropped from programming and they have to be reinstalled. I had Brain in the Jeep for 2 days before I could get appt. during that time Key got left on Acc or something happened and Batt went dead. Low idle ckt dropped out of programming.... wouldn't idle bvelow 1500 and up as high as 2500.
But the short of it is that reprogramming ended all that mess and been running and shifting great since it relearned its parameters and settled out - 2 weeks about. That was 4k ago.

Thanks for the kudo's... yeah, I'm committed to the board, trying to help where I can and I hope you, as well as, come back to help other pore slobs, like us... who are going through this dealer issue Shiit.

Damn... I wonder... if when disconnecting battery to work on the car is screwing up everything if low idle circuit is dropping... "Low idle ckt dropped out of programming.... May have been the final answer to the problem, as mine got to a point that it would not start at all. Had it towed and finally replaced with rebuilt PCM with warranty but was not told of the problem with the old PCM....Hummmm


Per you... Really good stuff!
It is my belief that there are fixes in this latest update that Chrysler isn't really admitting to. the update is a warranty/recall no charge item as far as I know...that is: It didn't cost me anyway. Installation took 30 - 45 mins. w/ several checkpoints along the way. The Mech I was dealing with told me a battery going flat on these Jeeps causes ckts to be dropped from programming and they have to be reinstalled. I had Brain in the Jeep for 2 days before I could get appt. during that time Key got left on Acc or something happened and Batt went dead. Low idle ckt dropped out of programming.... wouldn't idle below 1500 and up as high as 2500.
But the short of it is that reprogramming ended all that mess and been running and shifting great since it relearned its parameters and settled out - 2 weeks about. That was 4k ago...

again good luck

If the flat battery is a major player in the problem the alternative to "killing the brain" ,as we used to call it back in the 80's n 90's, is to take a jumper battery of low amperage 6-10 amphr (mower battery) and insert 12 volt adapter plug into cigerette lighter; thus keeping brain warm but not hot enuf to jolt the bejeepers out it. Yes you have to be careful plugging and unplugging connectors and u still have to use Digital everything (ohm/volt/amp/continuity) meters.
The procedure works like this: insert the jumper battery into the cig lighter and then disconnect main battery, do not let + terminal touch ground (which is not a good idea at any time because of residual power in the brain cud back flow to ground and disrupt internal circuitry). Then after the battery is reconnected remove the jumper battery. This procedure was used in all practices to retain parameters while changeing starters/alternators/engines and many operations. While using this setup just put the common test light under lock and key!! U don't want it around the vehicle, bacause it could cause havoc and also drain the little battery fairly quickly. The pcm will consume energy and deplete the jumper battery in two days;don't quoteme on the time span-keep an eye on the volts left in the little guy. Iffn u still need it hooked after that time use a 1 -2 amp charger on the jumper battery to restore it and maintain it. I know we are talking Jeeps here but there are worse vehicles out there when it comes to brain trubs...nthats as far as I will go with that. Any q's look me up in the profile section and email me.
This has been a real corker of a problem to nail down and it has taken many brains put together and many manhours to assemblre this database. EVERYONE'S input from both sides cure and problem/comments has been appreciated. no one is right and none is wrong its what it is. thanks to all !!

MM

Don't mean to seem like the school monitor on this site but I've been watching and helping where I can... Hopefully it is people like you who will comeback and stay with this site to help others, like your last post...
thanks for your in-put and hopefully someone will read it and benefit from your experience...
Cat5 Cane

Thanks for the update and historical review. Could you clarify your conclusions and actions? How many wires? and what firewall hole? Just the wires to the Crank sensor? Thanks

Sorry for the delay in response, back to school & kids are to blame. The linkage is only visible from under the jeap, on the drivers side and at the firewall between the tranmission bell housing, near the top of the engine. The linkage passes out of the firewall and is inside a flexible heat shroud.

It routes down to the transmittion, but not before bumping the wires on the Crank sensor which also mounts at the top of the bell housing. I am speculating that not all linkages move as much as mine (maybe it moves less/more based on it's origial manufacturered length). But if it moves enough to hit the Crank sensor wires, then over time it can damage it.

The crank sensor is a single cable with 3 wires, which connects thru a quick dis-connect to the harness which goes to the PCM. All of this occurs in the lower left of the engine compartment (when looking from the front of the radiator toward the engine. Please keep in mind that this is also where the oil filter connects and sometimes during oil changes, mechanics can get rough and bump this harness as well.

Good luck hunting.

Hi, I've been reading the posts here with great interest as I too am experiencing the random stalling with my 97 GC 4.0l 6cyl. I tried most suggested except for changing out the PCM. Backing out the screws helped for a while but then the stalling came back.

I was just wondering, what triggers the PCM to shutdown the engine? Is it the ASD relay? I'm not electrically inclined, but a relay is a switch right? So is it possible to just short-circuit the ASD relay to make it never trigger a shutdown?

I'm just speculating here, so correct me if I'm wrong. I wouldn't know if it could lead to dangerous situations when messing with the ASD relay. But I can't think of more dangerous situations right now than driving my GC on the road with the random stalling... Just want to stop the stalling once and for all, this is getting frustrating. Maybe the more knowledgeable members here could comment on the above. Thanks so much for sharing.

To Flying kick

I'm sure I will not do this answer justice... but short cutting the ASD is a bad idea... Jeep is so dependent in everything working properly that shortcutting anything to the PCM probably will resort in causing something else to get bad reading and then effect something else. Consider the PCM control unit is like the brain and if you should bang your elbow into something, a pulse is sent to the brain and then the brain tell the hand to rub the sore spot...LOL it's basic, but that's about the gist of it when comparing it to the PCM. Now if your taking medication (shortcut) and you bump the elbow, you might start picking your AZZ...LOL ...Sorry I couldn't help it!

PCM's... Keep in mind when you disconnect the battery, it wipes out the codes and memory for several days to a week or more and during that time the car goes into default mode (original setting) and the car runs like there isn't a problem... communication to and from the PCM starts from scratch and the car, most of the time, runs normal until the PCM starts getting bad reading from the bad parts, that are sub-par and then the PCM reacts by telling another part to change to adjust to the demands needed... Gas to air mixture is a perfect example of screwing up the PCM reading... Then when you get a diagnostic code from a scanner it could be for 4 or 5 different parts.

But that just my opinion... good luck

Just My Opinion

in respect to jumping out ASD relay,,, it's ok for diagnostics when u have a problem tripping constantly. however there are dangers. the relay is there to protect the pcm; operator of vehicle and circuitry. I think if uread all the posts that it is mentioned that this vehicle is built like the NASA shuttle. the main funtion of the relay os to shut down the fuel and ignition systems in certain conditions... wreck, rollover, and theft. I used to believe this was a major source of my problems of 18 months of chasing; however I slowly had to admit after many dead end tests that it was not the source of most of my problem. but I did find that the relay was weak and causing some problems.. so I replaced it.... less than $10. My mate looked at me and said " 1500 dollars of testing and tracking and and hair pulling and then u spend 10 bucks and end all that fun.... I don't get it. the moral of the story is look sniff check and then see how mucvh to circumvent the problem and then proceed. Also go to Jeep and get the relays .... there si a difference. If u just can't bring ur self to do that then check Autozone.... they claim to have OEM electronics parts....I can't tell the difference and have tried them. Alas there are a few I went and got Jeep parts afterward because I couldn't take a chance and needed closure on that part.
ALL MY PROBLEMS BOILED DOWN TO A BAD PCM , that was dropping circuits out. Replaced and went to dealer for programming and updates; a real must. END OF ALL PROBLEMS.

Me again... Just to say it again for the 100th time... My learning lesson learned was to buy Mopar parts from Jeep... forget the discount parts houses except for simple stuff like distributer caps, plugs... etc.

Thanks for the quick replies and advice, guys. Much appreciated. Don't get me wrong, I would continue to find out what is wrong with the car. Just that using Cat5's analogy, if I bumped my elbow, I'd like my brain to go ouch. Not put me in a coma? I know the car is functioning okay, just not according to the brain.
Anyway, thanks again and I'll continue looking for a remedy. I'd hate to see Jeep go, there are some sentimentals attached. I wonder if chrysler is aware of this 280 post thread...

Hello to everyone,

I've got way too many posts on this subject already so I'll try to keep it short. The ASD relay is controlled from a switch inside the fuel tank and shuts off the battery voltage to the PCM in the event of a roll-over. Although it is possible for it to fail, it's unlikely unless the vehicle's been flooded or stored in a very damp area for a while. All of the other relays in the box are identical. Swap them if you're suspicious. If the problem moves, bingo!

With reference to the resetting of the PCM by disconnecting the NEGATIVE terminal of the battery for a short time, that is good information, HOWEVER, it's a computer, guys, it starts working again IMMEDIATELY, and if there's a fault still existing, it will immediately detect and display it 1 second later. That's it's job! And yes you can disconnect the positive battery lead and accomplish a reset. Just leave it off long enough for any capacitive load to fully discharge, letting the PCM voltage drop to near zero volts.

At the risk of being overly repetative, use the following logic: If no codes are stored and readable in the PCM, there IS a failure in either the battery voltage going to it or inside at the connector pins of the PCM. This problem is VERY likely in the 'A' connector of the PCM, that's the one toward the driver side. PUT FIRM PRESSURE from your thumb against the top driver's side of the PCM. Move it 3/8 to 1/2 inch toward the firewall at the top driver's side. If the engine stops and (if the problem has been intermittent and unpredictable failures with restarts fairly quickly and no codes stored) it will, this lets you know to a fair certainty that the PCM is bad. To confirm your conclusion, force the top driver's side of the PCM forward a half inch or so. Use whatever you've got, but a 3/4 inch hot water PVC elbow works great. You will almost certainly find that it is now virtually impossible to cause the failure by pushing rearward on the PCM. THIS DOES NOT FIX THE PROBLEM!!! It's only a troubleshooting tool. This is a very dangerous problem that needs immediate and conclusive repair. Don't waste your time trying to repair the PCM. That requires special skills and equipment. The ONLY other likely possibility then is that the PCM is losing either Battery positive or negative links. The KEY IS WHETHER OR NOT THE PCM IS STORING ERROR CODES. Although it is possible that the PCM could see and store an error code after it lost battery voltage, it is not likely that this would be consistantly the same, time after time.

Finally, this is a VERY COMMON failure with this vehicle. Replacing the PCM can be tricky, as many of the ones in junk yards have the same problem. If it's been hit in the rear, be very suspicious. Buying new is expensive (~ $700)and there's no guarantee that the same problem won't recur with the new one, at some point in time. If you buy rebuilt, make sure you have a lifetime warranty and hot-swap, in case the first one you get doesn't work. I'm assuming your computer is a 406 AB model. The 406 is the engine size and cylinder count. The AB is the model scheme for the CODING. IT is my understanding that only an AB or AC core can be reprogrammed to run this engine and vehicle. An AD will start the engine but will not RUN after you release the starter switch. I'm almost certain that Chrysler (Yeah, they built your Jeep) has a universal blank they can program for you, but even if you found a used one, you'd likely have to have it reprogrammed by them or someone else with the proper (fairly expensive) program flashing gear.

Reference to the relay quality OEM VS after market: They're all made in China now, so there's likely no real difference. A relay is either activated or un-activated. A spring holds it in the open, unactivated, position and the magnet created by an activating signal holds it closed or activated. IF the vehicle rolls over the relay removes voltage from the PCM, removing fuel and spark. Barring wiring problems it is unlikely that your problem is in that relay, anyway.

There is a seperate and different problem with this same vehicle, on the 'C' connector that causes the transmission to not shift into overdrive. This is usually broken pins inside the cable connector, and not inside the computer itself.

Hope this helps. Remember, this car like all others, works on simple mechanical and electronic principles. I will say again this time, the cutting off of a portion of two screws and other such voo-doo is not fixing this problem. It is simply that you have removed and replaced the connectors and something mechanical has been moved and the power through the connector is temporarily restored. Last, What is the actual problem? On the five units I have dismantled to inspect, the problem has been a broken printed board etching at the voltage into the PCM printed circuit board. If memory serves correctly it was at pin A-32, 33 or 34. No matter, it's not field repairable anyway.

Regards,
Jim

Ha! Ha! Ok, kind of a teaser.
I found this amazing forum nearly a year ago. Gained immense knowledge and kept myself on the road (sort of).
I've posted a few and been reading with time.
After all the cash, time, energy, stress and so on, I HAVE indeed solved my Jeep issue........I'm getting rid of it!!!!!
I got a Toyota Tacoma, gonna' put the Cherokee on the side of the road and hope I can get a few bucks for it. It looks great but there are still goofy-*** things going on! What haven't I replaced and it continues with troubles? I'm done...never again will I drive a Jeep! Friends shake their head and say, "I told you they're crap", or, "yeah, isn't that what you do with Jeeps...fix things all the time?".

Side note........ been looking into ethanol(most of us have no choice but to put it in our cars). My stalling persisted so I added a fuel injector cleaner after hearing a couple mechanics rail on about how ethanol screws up engines. Anyways, the engine began stalling even worse. My thought is that the ethanol loosens up crud, then the cleaner does so as well, hence clogging fuel filter.
In looking at info about ethanol some vehicles do react badly, or is it methanol??? Anyways, lots of varying thoughts on this. I will be getting the fuel filter cleaned in the next couple days---can't sell a car that doesn't stay running! Hopefully the filter is clogged with junk and Jeep will continue to run. Could this be a source of some of our issues?????

Hello to everyone. I've enjoyed working with this post for several months, but I must move on.

With reference to ethanol, you will almost always find the inside of your engine much cleaner than with 100% gas. All modern vehicles adjust the timing and other thingies for the fuel you run. It's hard to make a case for ethenol causing any problem.

Every GCL I've ever been involved with has no fuel filter other than the one in the fuel tank on the inlet to the fuel pump (fuel tank must be removed to access it). WORTHY OF NOTE is that the constant on and off mode of the PCM failure can cause the fuel pump to fail prematurely. The PCM computer is 'chattering' a lot more than you think. It's only when it fails for a long enough time to cause the engine to stop running that you become aware of the problem. PREMATURE failure of the ignition components can also occur because of the problem. The PCM computer typically fails in the 150,000 to 210,000 mile range. Any way you look at this failure, it's going to come back to a defective PCM, and on inside of the 'A' connector, 99 times out of a hundred. All of the other failures are either parts changed that were not bad or ones that had failed as a result of the intermittent PCM. MOST of them were NOT bad, IE, they did not make the vehicle run better

Having owned a few Chrysler products myself in the late seventies and early eighties, I'm no real fan of Chrysler products. However,this series of Jeep GCL really is not a bad vehicle at all compared to some others, once you get past the type of problem that is occurring here. The key to solving this type of problem is to admit that when you replace a part and the problem remains that part MAY NOT have been bad. Likewise when you replace one and the problem gets worse, there sre compatibility issues. The worst issue with this problem is that it's hard to know whether you're replacing a bad part with another bad one. That's when you begin looking for things that don't make sense. I have successfuly repaired this problem on 11 vehicles. I lost a fortune in hours and parts on the first one. The next ten went like clockwork.

Good Luck to all! Jim

Yes, the pcm is a computer and it starts working immediately, however it collects data before throwing out instructions, and the data is averaged over a certain amount of time/miles. You may notice after changing a bad O2 sensor that it takes a little time for the check engine light to turn off. And if you were to plug the computer in for a smog check immediately after a "fix", it would fail and the smog guy would tell you to go drive on the highway for an hour.

<<I wouldn't know if it could lead to dangerous situations when messing with the ASD relay.>>

It costs 10 bucks. If you have doubts, just plug a new one in.

ASD Relay-in case of a rollover the ASD Relay is a safety device, which shut down all electricial power to the engine.

Purchase or borrow as scanner, will save time,money and crazzness!
Has the crankshaft sensor been replaced? check the charcoal canister could be bad, take ASD relay and switch it with the fuel pump relay,
trying to duplicate the same acceleration condition. Try swapping out different relay in the PCM one at atime to duplicate the situation. High milage vehicle 90,000 mile plus, relay have a coil contacts inside and can be pitted from electricial current which wear out from switching on and off. I have purchased a 1996 JGC factory service manual from ebay. I also have a scanner. From working on my daughters 96JGC w/175,000 miles, I have replace the crankshaft sensor
and the ASD Relay. Hope this helps some!

Hate to say it but it could be a simple Gas flow issue or fuel/air mixture (O2 Sensors), could be clogged fuel injectors, ECM/PCM.

Your back to square one... Try simple gas treatment additive like GumOut or Lucas... cleans fuel injectors and gas lines... It worked for me. Put in before gas and fill to 1/2 tank (strong mixture).... You'll see difference

Why Do Catalytic Converters Fail?
There are a number of factors that affect the performance of your catalytic converter. The converter works in conjunction with your oxygen sensors to come up with the cleanest possible exhaust. As long as everything is operating as it should - engine at proper operating temp, air/fuel mixture optimized, no contaminants added to the exhaust - the system works really well. Throw a faulty O2 sensor into the mix and you have problems. Since the O2 sensor can alter your air/fuel mixture, it can kill your catalytic converter. If the mix is too lean, the converter won't have the right elements to clean the exhaust. Too rich and the converter will heat up to the point of melting, and trying to push exhaust through a solid block is tough. If your car burns oil or leaks coolant into the engine, these contaminants can collect on the ceramics inside the converter and cause it to clog.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Another source...
Troubleshooting DIY RepairsAuto Basics Troubleshooting Problems With Your Car
By Matthew Wright,... About.com
http://autorepair.about.com/od/troubleshooting/u/path_Troubleshooting.htm#s
Guide to Auto Repair

The key to good auto repair lies in troubleshooting the problem. If your car won't start, there are a number of things that could be causing the problem. Proper troubleshooting will eliminate potential issues that aren't the real problem and point you in the right direction. There's no bigger waste of money than repairing or replacing an auto part only to find out it wasn't the problem. These troubleshooting tips should help out and save you both time and money, not to mention frustration!

Basic Troubleshooting
Electrical Problems
OBD (On Board Diagnostics) Evaluation Basic Troubleshooting
Troubleshooting has to start out simple. Basic troubleshooting focuses on the most common problem areas in auto repair, and provides a good starting point for searching out what repairs need to be made.

OBD (On Board Diagnostics) Evaluation
Modern automobiles are equipped with their own troubleshooting systems called On Board Diagnostics, or OBD. These systems take thousands of readings from your car's sensors, continuously compiling information about how everything's working. When something is awry, the system sends out a code telling mechanics (or you!) what's gone wrong, and often triggers the dreaded Check Engine light. Unfortunately, the language of OBD and OBD-II systems is a bunch of numbers. Use our guide to figure out what your error code number means, what sytem it's talking about, and what you need to do to fix it.

In a word: Its your PCM, no doubt.
Everything else is a symptom, causualty, but not a cause.
I would get a new one from Jeep, not a rebuilt one, or I would sell the Jeep.
I have been thru all of this, every bit of it. My second rebuit PCM has done fine. It stalled twice and I will have that doubt forever, that it will happen again when i least expect it. And that doubt takes every bit of fun out of taking this great Jeep to the next level... lift kit, backroad trips, etc.
Good luck
dw

I have been following this thread for over a year now, having had all of the stalling problems, etc. with my 97 JGC Laredo. I had replaced everything imaginable when I finally purchased a rebuilt PCM (from O'Reilly Auto Parts with a lifetime warranty) a little less than a year ago. This corrected all of the problems with my Jeep and it has run fine until a couple of months ago. It started with the emgine revving to high RPMs when sitting in neutral or when cranked. It wouldn't do it everytime, and has not done it for several weeks now. That problem has been replaced with random hesitation/sputtering. I will be driving at speeds anywhere from 45-65 and it will start sputtering and jolting, like there is an issue with it getting enough fuel. My dash lights have also started dimming randomly. It has NOT stalled (yet) thankfully, but I am concerned that it will. Can anyone tell me if this could be the symptom of the rebuilt PCM having problems or is there something else I should look at first before swapping it out? I have a one year old child who's safety I am concerned about and financially buying a new car is out of the question. Thanks to all of you who reads our posts and try to help us out!

I once had this problem with my 1997 JGC, a few years ago.. I removed the dash light switch/dimmer module and found that the printed circuit board copper traces were braking right at the big main connector. I ended up adding jumper wires from the pins on the big connector to the slider potentiometer pins and to any other pins on the other electronic components on the printed circuit board. I would bet money that this is also whats going on inside our beloved PCM. Chrysler probably farmered out the electronics work for there electrical parts to the lowest bidder during the cash strapped years of the mid to late 90's.

Incidently the problem is back and I have to take it apart again and add on more wires where more traces have broken..

The way to test it is if you push on the slider and other knobs on that panel the display will come on and off and flicker. By pushing on it you flex the broken copper traces to make intermittent connections.

I did the same thing to many PCBs for machinery too. The problem is that the cable is susceptible to vibration and the PCB is not. The pins are mounted to the PCB and the joint takes all the abuse. I used to take 30AWG wire unjacketed and cut about a 1/2" piece to bend it in half and make a loop in the middle. The wire is thin and this fits right over the typical trace. I would scrape, lightly of course, the coating off of the trace and just solder the "hairpin" looking loop onto the hole and trace lead. Just make sure the loop will allow the pin to fit through. This happens to heavier components mounted on those PCBs too. Transformers, large caps, coils, and transistors with heatsinks. The big problem with the PCM is partly due to either the caps or the connector losing connection. If you look at the PCM with the cover off you will see the caps have separated from the potting compound and usually the transistors too. It could be heat related, but my bet is vibration had a lot to do with it, which means the joints are in question.

bad news no doubt... pcm can be reflashed. however u need a two way scanner AND a password to the Chrysler website to download data for reflash which will automatically give u critical updates. I do know, from my own experience, that the pcm can drop circuits from something as simple as a dead battery. I had to change pcm three times until got one that would work, then forgot the key in acc position the nite before I had an appointment at (cringe) the dealer to get the vin and mileage entered to pcm. when I finally got it started it had dropped the idle circuit and was not timeing correctly all the time. The tech confirmed this when he reflashed it and put several updates in for me.. ablsolutly no problems since then and things have been getting better all the while for 5 months. Evereytime I put the critter into a new condition it continuously learns and performs better he more it experiences the new condition... old brain didn't do that so well. this might not help but when I found that NONE could help reflash but the dealer and I had a choice between a 3 star and 5 star dealer with a price diff of $50, I decided with all my troubles in the past; what was another fifty and went for the 5 star dealer. Test drove a new jeep and applied for loan to get it and got the reflash for free. But that was last July. GOOD LUCK... IFFN IT IS ANYTHING BUT THE PCM U WILL GET CODES THAT WILL SHOW UP IN THE DIAGNOSTIC MODE..UR 97 IS THE SAME AS MY 96.

"i have ( HAD ) a 97 cherokee with a 4.0 that's not getting any spark. i have replaced the coil and checked to see its getting power (my test light will light up on GREEN / ORANGE and when i flip the tester to + i have ground on GRAY / WHITE (just not while cranking) i visually inspected the cap and rotor / cleaned all contacts with sand paper (as well as all relays under the hood) and checked injector pulse. all the gauges work on the dash and the info cluster. all the fuses are good under the hood and in the vehicle. the fuel pump kicks on fine. i was told that if the crank sensor is good then the 3 wires should test 1 as a ground 2 should have 8 volts and 3 should have between 0.3 volts and 5.0 volts but when i tested it with my volt meter i was getting between 5v and 0.3 v on one wire and between 3 and 4 volts on the other so i replaced the crank sensor because it should have 8 volts on that wire (but it didn't solve my problem). so i have also pulled the codes ( key on key off key on key off key on and count the blinks of your check engine light between pauses, if you have a digital odometer it will tell you the codes) and they are reading 12_54_55. 54 being the cam sensor which is inside the distributor on this model and year jeep aka sync signal generator and its called the IGNITION PICK UP COIL at your local parts store, and swapped it out then i disconnected the neg. batt terminal and removed the coolant reservoir and pulled the 3 plugs from the pcm checked the terminals and tested the gray / white wire (-) from the pcm to the coil itself to make sure it wasn't damaged THEN I FOLLOWED THE INSTRUCTIONS BELOW AND now i start and run beautifuly. WHAT A PAIN IN THE BUTT!! and this is the link to a jeep site that explains your vehicle sensors and how they work. good luck

http://www.jpmagazine.com/techarticles/engine/154_0608_1987_jeep_wrangler_xj/ind- ex.html

Short story long: I have a 96 Grand Cherokee 4.0L, 125,000 miles. Several weeks ago, I started to have stalling issues. Hot or cold, dry or wet, first drive of the day or last, it didn?t matter. The engine would cut out. It felt like it lost all electricals.
At the time it was showing an ASD relay code. Swapped the ASD and A/C relays. Same problem. I didn?t have time to look at it, so I had the dealer go through it. After 2 days and $200, they called and said it was the ASD relay, and that they put in a new one, and it?s all good. Um, ok, maybe I missed something. I?m a trusting soul, but let?s see if this fixes it. The next day the problem was back. I went back to the dealer and they basically said, ?We don?t know what it could be, good luck with that?. Now my wife knows why I don?t go to the dealer. By the way, the old relay tested good.
My turn. Being the methodical aircraft mechanic that I am, I grabbed a multi-meter, contact cleaner, and wiring diagrams. I cleaned connectors, ohmed out wires and sensors, checked for power and grounds. Everything checked good. By now, it?s showing ASD, crank sensor, and primary ignition codes. Then, with my wife trying to start it, I wiggled the connectors on the PCM. Every time I wiggled the gray C3 connector just right it would run. When I let go, it would die. So I took the connectors apart and tightened up the crimps (I don?t recommend doing this without the proper extractors and crimper). Threw it back together and BAM! Same problem. Well, time to bite the bullet and check for bad solder joints on the PCM board. I took the cover off of the PCM and realized that looking through the potting compound is like looking through Guinness Stout. But, I put it back in and hooked it up. It started stronger than ever, and didn?t even think about stalling. Yes! I figured that I finally got the connectors sorted out, so I left it over night to cool down. Got up the next morning and it started right up and wouldn?t stall even when wiggling the connectors. So I put the cover back on, put the PCM back in, hooked up the connectors, and BAM! It wouldn?t start! That was the point when my wife asked, ?How?s it going?? And I, being the methodical aircraft mechanic that I am, said, ?what the ----?? That?s when my wife turned around and went back into the house. While smoking a pack of cigarettes, I thought, ?Gee, it runs with the cover off, but not with it on.? DUH, wonder what it could be? So I backed out the two screws that hold the cover on and BAM! It started right up. Then, while it was running, I tightened the outboard screw and sure enough, it died. Yes! Aircraft mechanics love it when they can make things stop working. I installed new screws (1/4? long, factory screws are 1/2? long Torx head), and she?s been running great ever since.
Now, will this fix a bad crank sensor or idle air motor? No. But it is an easy trick to try before going to the dealer and having them throw expensive parts at your Jeep and seeing if any of them stick. Just back out the cover screws about 1/8?-1/4? (don?t worry, nothing will fall apart inside). If it fixes it, great! Spread the word. If not, use logical trouble-shooting steps. Learn the systems ? what will and what won?t cause the problem. Good luck.
As a side note, if you want to see a service manager?s eyes pop out of his head, tell him that you want your money back because your not going to pay them to trouble-shoot a design defect. It?s a glorious sight.