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Jeep Grand Cherokee PCM Module Replacement

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  • ya on the scensors there is really no fuse for protection i have been thinking about throwing my own inline fuses in so i dont go through this again the only fuse for protection is the engine control fuse but it feeds so much stuff and miles of wiring

    but mine is still not running i pulled my fuel pump and thats it it got cold and started snowing so im trying to get enough room in my garage to keep trying

    but good job im happy to hear its fixed
  • Man it sounds like there is a lot of problems with your jeeps. OK now I have one for you. I own a 2001 Jeep Grand Cherokee Laredo. The battery and alt. or both good. The jeep turns over just fine but wont start all of the time. If I keep playing with the key as in turning it on and off a bunch of times finally i hear the fuel pump kick on and it will start. All of my gauge lights come on but the gauges are dead unless the fuel pump comes on then the gauges read fine and it will start. I also notice that when the fuel pump turns on the light with the key and a line through it goes out but when it don't the light stays on. When i get the jeep to start it runs just fine. I don't think its a pcm problem or it wouldn't run at all would it? If it was the fuel pump then it would shut off while im driving it wouldn't it? Any help would be greatly appreciated. I see that some of you had similar problems but I didnt see what the fix was. Sorry so long but I wanted to let you know all of the info that I have. Thanks.
  • Ya it sounds like you have a short somewhere off your ignition wiring. On my 1992 jeep i had a short in the park/neutral switch wiring and it did exactly what your talking about. my 93 is doing almost the same thing and i am still trying to locate the short
  • Hey
    I had a 1998 JGC Laredo that I loved vary little problems, sold it and I have a 2001 JGC laredo V8 auto, that I just got,here's the problem, It starts great when cold but when it runs for a while and I shut it off I have to crank it longer then I did when it was cold sometimes longer then others, and it lopes (studders) when I stop at red lights sometimes. I changed the plugs, no distribitor or rotor. I get from reading in the forums it sounds like it might be the Crankshaft Position Sensor? How do I locate it an is a pain to do ? And what about the Oxygen Sensor? Thanks
  • I would test my oxy sensor first then camshaft and crankshaft sensor
  • Thanks I will. Do you know where the Crankshaft Position Sensor is located? And is a pain to change. Do I have to jack up the front end?
  • on my 93 jeep the crank sensor is right behind the engine on the flywheel and yes it is a pain to get to but you can test it with out pulling it. just need to find the wires that go to it and make sure you are getting proper signal from it
  • Hey
    I found the crankshaft position sensor location on my 2001 JGCLV8, right behind the starter, had to jack up the front end and pull the starter, bingo, there it was. changed it, seems a little better on the idle side.dosent seem to be as rough, time will tell. Maybe it dosen't seem to crank so much when I go to start it when it's hot !!!!!!! Will post later when and if it is at all better If any other ideas on what I should try per original post please advise.
    Thanks for the replys
  • I have a 2001 JGC laredo V8 auto, that I just got,here's the problem, It starts great when cold but when it runs for a while and I shut it off and wait about 45min to a hour it starts hard ( Have to crank for around 10 12 seconds is this normal ) have to crank it longer then I did when it was cold sometimes longer then others, I changed the plugs, no distribitor or rotor. I get from reading in the forums it sounds like it might be the Crankshaft Position Sensor? Changed the CPS seems to run smoother but still starts hard when hot What if the battriey is smaller the the orignal? Thanks
  • 03fxdwg03fxdwg Posts: 2
    4.0 L with about 150,000 had distributor bushing make screeching nose. Had distributor assembly, wires, cap, rotor and plugs replaced and by independent shop and vehicle began to die while running without any warning. Just seemed as though someone cut off the fuel or there was water in fuel. Live in SC and checked with stations where I fill and used many cans of gas dry without any change. Engine starts back up and runs as though nothing happened for seconds, minutes, hours or days. Had distributor replaced again but problem persisted. Took to Jeep dealer and and had error code for crank position sensor throttle position sensor. Replaced them and then had error for bad PCM. Replaced that with Mopar part and dealer went on to have injectors cleaned, coil replaced after error code showed, Replaced battery and cleaned cable connections. Dealer replaced fuel pump and distributor primary field assembly and problem still persists. Will backfire and miss at speed, stalls at idle or under acceleration or while coasting. Sometimes engine will fire back up and other times I have to coast out of traffic. Sometime when cranking, then engine speed will increase like it wants to run, but isn't getting enough fuel or the spark timing is off. It will usually start right up if you turn off ignition and wait for 15 to 30 seconds, but that is had to do if you are sitting in the middle of an intersection with cars coming at all directions. Dealer is at a loss (no new error codes even though I had a solid check engine light for a day a week ago and then it just went out the next time I started the car. Dealer is replacing PCM under warranty as I have spent over $2500 in the past 9 months.
  • 03fxdwg03fxdwg Posts: 2
    New, new MOPAR PCM handled under warranty. Has run without a stall, stutter or back-fire for 9 days. Should have made them try that last August.
  • I have finally got back on to post. the sign in button has not workrd for me for like 3 months. Anyhow i finally found all the issues with my 93 grand cherokee. First i had a short on the power supply to my coil that was touching the frame creating alot of other problems. second i found another short between my tranny and the body coming off the main harness going to my oxy sensor-this one sucked as i had to pull the tranny just to find the short let alone fix it. luckily none of the shorts fried my pcm but every shop in town told me it was my pcm-except for the napa shop they are the ones that told me i had multiple shorts to just replace all the wiring harnesses in the jeep. instead i just rewired it my way the right way. and runs like a charm for having 230,000 miles on the engine
  • jkalvinjkalvin Posts: 2
    Can anyone possibly tell me exactly how to find and replace this sensor? I have an intermittent stalling problem. I have checked the fuel pressure and replaced the following:

    Throttle sensor
    Cam Shaft position sensor
    Rotor
    Distributor cap
    All wires
    Coil.

    The dealers have said that I should be able to R&R this sensor without removing any other parts. I can find, what I believe is an oil sensor next to the distributor. Then, behind this, close to the firewall, there is a cable, leading to a connector, which looks like the replacement part I have, but I am not positive it is the correct connector. (The replacement part has some specific markings on the outside, which are not on the part on the car. Is this important?)

    I am not able to see, nor feel the othe end of this wire to confirm that this is the correct sensor. If you have any photos or clear instructions on how to get to this part, I would greatly appreciate your help.
  • rev4revrev4rev Posts: 11
    Changed mine on a 94. I believe the dealer fibbed to you. You have to remove the oil sending unit and emission tube just behind and below the oil pressure sending unit. Then plan on some skinned knuckles working back there. That is what the repair manual said anyway and I tried doing it without removing that stuff to no avail. I even thought about boring hole in firewall and coming thru there to get to it but decided on skinned knuckles instead.
  • rev4revrev4rev Posts: 11
    Oh also the replacement one i got from the dealer was thinner and they told me to just use shorter bolts. not sure about markings.
  • jkalvinjkalvin Posts: 2
    Thank you so very much. I will give that a try. I spent hours yesterday trying it from the side of the valve cover, and earned numerous scratches and scraps and lost a 1/2" socket.
  • toledtoled Posts: 1
    The yellow light sign in the control panel stays lightened up with any of both original car keys of my cherokee classic 2001.With this light on car wont start.
    I have a friend who had same problem and in the chrysler service shop told him the PCM had to be replaced.

    Have any of you experienced same problem and solved it without replacing PCM?
    On other hand i've checked pcm sales on line andt they require the VIN number.
    What is the VIN number and where do i find it?
  • axe41axe41 Posts: 2
    I have a 1996 Jeep Grand cherokee Larardo 6 yl. It wont start but it turns over. Im getting no spark. Checked the coil and it is not getting power to the coil. Someonoe suggested changing the Power Control Module (PCM). Before I do that is there any other suggestions that my work?
  • i would check your auto shutdown relay your engine fuses and test ohms from the battery to the positive side of the wire going to your coil for shorts first but usually if there are shorts going to your coil they take the pcm out so check for those first before replacing the pcm
  • axe41axe41 Posts: 2
    thanks i will try that out and let you know how it works
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