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A very similar case to the Dodge Neon we just did. https://www.youtube.com/watch?v=Pin9g7rHFPo&t I think you will see the only difference is in this case the 5v ref was still there and functioning. -Enjoy!
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50 thoughts on “Jeep grand cherokee: no start / no communication”
  1. Avataaar/Circle Created with python_avatars Steve Henderson says:

    Had same problem. turned out all 3 wires to camshaft sensor were bare and shorting together at connector end. new connector, no problems.

  2. Avataaar/Circle Created with python_avatars Lisa Doc says:

    Need help having week power to my coil …got a jeep 5.2 v8

  3. Avataaar/Circle Created with python_avatars a1_anonymouss says:

    I can't tell what wires you are testing in the video where is the close up of what you are doing?

  4. Avataaar/Circle Created with python_avatars powerof3online says:

    how do you bypass the pcm on a 2002 jeep GC 4.7 Ho

  5. Avataaar/Circle Created with python_avatars Derek Mitt says:

    Hey my Jeep Grand Cherokee Laredo 3.7 awd sometimes shacks and sputters like crazy when I try and start it. Wondering if you might have an idea why it may be doing this? Thanks

  6. Avataaar/Circle Created with python_avatars jbeez says:

    How do you get the connectors out of the way to be able to back probe the pcm?

  7. Avataaar/Circle Created with python_avatars Albert's Auto Diagnostics LLC says:

    I'm working on a 2006 5.7 and its got every light and code in the book when I put KOEO every single relay starts clicking like crazy im lost

  8. Avataaar/Circle Created with python_avatars Romeo Ortega III says:

    My 04 Jeep WJ 4.7 quit.
    It was displaying P0340 camshaft position sensor.
    So I replaced both the camshaft and crankshaft sensors.
    Fuel pump was weak as, you know.
    Put a new BOSCH fuel pump great pressure.
    No spark still getting the same code P0340.
    Looks like will be going to the shop with it.
    My little scan tool (Blue Driver) is meh…
    The PCM powertrain control module is listed in the possible causes..
    Thanks for your time.
    Just for fun and excitement going to try wriggling the wires and pull the PCM/ECM open it up for a visual inspection.

  9. Avataaar/Circle Created with python_avatars Brian Burnett says:

    i just found a fuse that will do same problems , but start after fuse replaced under dash is on 11 or 12 un marked ,with being hard to locate . but critical to skim , no code blocked out ,same deal.. took 3 weeks to find fault .

  10. Avataaar/Circle Created with python_avatars Joseph Bennett says:

    If I have all the same symptoms and have verified all the same voltages but can’t test for the PCI a is because I don’t have an oscilloscope would I be pretty safe to say I have a bad PCM also? Thanks

  11. Avataaar/Circle Created with python_avatars Mohammed Abdullah says:

    What pins did he check? Thanks for the help anyone!

  12. Avataaar/Circle Created with python_avatars Brian Knappenburger says:

    I have a 2002 WJ with the exact same issue except I am on computer number 5. Did this ever get corrected by another ECM replacement? I have had the same issue where the new ECM would make the car run them it would do the same no start 3 days later. They are no longer warrantying my computers as they say it is another issue or it would never have started the car the first time..

  13. Avataaar/Circle Created with python_avatars Desert Mike DIY says:

    Some if not may years of the Grand Cherokee had bad solder on the ECM boards.

  14. Avataaar/Circle Created with python_avatars princemarcel says:

    How do we stop the corrosion?

  15. Avataaar/Circle Created with python_avatars Robert Smith says:

    ….my new 1995 Grand Cherokee Laredo had an aftermarket remote start/security system installed by the dealership when I bought the vehicle …this system was a continuous problem…..at approximately 100,000 km.the first PCM failed. A rebuilt PCM from Jeep cost me $1400 installed …that PCM failed after 10 months (12month full replacement guarantee)!….when the dealership installed a replacement PCM it failed immediately, so they installed another (4th PCM)…..
    I did a lot of internet research and found many Jeep owners had complaints of ‘no start’ or ‘stalling when driving ‘…..all occurring after vehicle reached 60,000 miles….some thought a change in programming of the ‘run’ software by Jeep incompatible with the older PCM was the cause of failure…….an Avionics Engineer dismantled a failed PCM and suggested the problem was caused by screws holding the PCM to it’s base….these screws were too long & made contact with the firewall……after sufficient miles the screw removed the paint from the firewall and grounded the PCM to the frame; giving it a negative charge!..many Jeep owners replaced these screws with shorter ones and found success in keeping the vehicle running….my replacement PCM’s were installed with shorter screws….

    …….ten months later all the old problems returned…..stalling….no start…the remote start/ security system had been turned off for many years but the dealership demanded it be removed entirely….I paid to have it removed….the dealer ship replaced ignition switch,starter,& got Jeep running….but I couldn’t trust it….began driving less…then battery kept discharging ….back to dealership to test electrical….found 0.25 amp discharge- 10times the allowable…..the parasitic leakage was traced to fuse powering the instrument panel including the RADIO!!…

  16. Avataaar/Circle Created with python_avatars Paul Runell says:

    why is it ok to use the headlight bulb for testing the power and ground not critisising just want to learn

  17. Avataaar/Circle Created with python_avatars Chad Gardee says:

    We are so luck too have Eric o every since his first video I been hooked very detailed videos

  18. Avataaar/Circle Created with python_avatars Kevin Baker says:

    You should send that ECM over to Big Clive for "analysis"

  19. Avataaar/Circle Created with python_avatars A LeBlanc says:

    Quick and accurate. Thanks Eric, gotta love the south, eh? :>)

  20. Avataaar/Circle Created with python_avatars MrOldandslow says:

    Love your videos. One question…is there a reason you don't use fender covers?

  21. Avataaar/Circle Created with python_avatars Shared Knowledge says:

    To roughly quote you: "He replaced the ECM, it ran for a period of time, and then died again with the same failure…" What better way to encapsulate owning ANY Jeep product made after 1968. Honestly Jeeps are Junk and I still can't believe you bought one for yourself after documenting just how awful they are in many of your videos like this one. They're JUNK designed and poorly assembled by drunken Frat boys under the watchful eye of greedy corporate cost cutters.

  22. Avataaar/Circle Created with python_avatars Moon Moon says:

    Tweaking the connector gives a massive clue. Crack the ECU open and there will likely be bad solder joints everywhere. These ECUs would be from the vintage where lead free solder was just starting to come into vogue but no one knew how to make it less shit yet.

  23. Avataaar/Circle Created with python_avatars Randy Moser says:

    Had a jeep 4.0 the cover screws to long eventually ate in to board. We're to long. Found an aviation mechanic found issue

  24. Avataaar/Circle Created with python_avatars Mike the Mechanic says:

    Every 2001 Chrysler truck product needs an ECM. I've put 6 or 7 in this year all were 2001. Mostly Jeep but a few trucks.

  25. Avataaar/Circle Created with python_avatars ToXZicK Gaming says:

    Dang Mr. O'….. You have been having the ECU Blue's lately. lol Great Videos…. as ALWAYS! Thank You Sir.

  26. Avataaar/Circle Created with python_avatars Dave Conway says:

    Grand Cherokee ecms are in a god awful exposed location. Expect to go through a few. Especially if you go off roading

  27. Avataaar/Circle Created with python_avatars Norby says:

    Hey eric , could you please help me what is your program that you use for car wireing diagrams and other goodness ? Thx

  28. Avataaar/Circle Created with python_avatars Doug Thielen says:

    Eric why not take covers off the ECM and check for bad solder joints to see if it fixes the problem.

  29. Avataaar/Circle Created with python_avatars Ethel Ryan says:

    The Chrysler bashing never ceases to amaze me. Even Eric's Hondas have problems. I wonder how many of us live in rust-free climates (our '74 Caddy hasn't a single spot) and haven't the first clue just how awful upstate New York's climate really is on electronics.
    Truly enjoy Eric's moonlighting videos. They're always a totally different mood.

  30. Avataaar/Circle Created with python_avatars Michael B. says:

    Eric you are just to good for the average vehicle, they don’t stand a chance..

  31. Avataaar/Circle Created with python_avatars demodulationseinheit says:

    Do you know for sure that the other modules making the activity on the com-line and not the pcm? You have to have it unplugged to rule out your pcm is talking to a broken wire…

  32. Avataaar/Circle Created with python_avatars haywire17 says:

    So basically, the problem is likely cracked solder joints INSIDE the ECM, where the pin headers go into the PCB…Probably potted in epoxy, and difficult to fix "to component level" by resoldering…

  33. Avataaar/Circle Created with python_avatars Thomas Griest says:

    What Eric O is not is NOT identifying is the fact that the wiring harness in the WJs are notorious to shorts, Let me go back to 4 yrs. ago when I purchased my WJ for a whopping $500 (couldn't pass that up, the 4×4 worked) my buddy just wanted to get rid of the thing. I looked it over,popped the hood and seen the "Big 4.0" SOLD. Got it fired up after sitting 2+yrs.and heard the familiar "the broken piston skirt slap" Oh Boy, here we go But it's cast iron block and head it's fixable. What I didn't know was the trans was burning up, so I found a reasonable trans and had it installed,little did I know that the sensor in the bell housing was yanked by the shop who installed the trans causing a short in the harness the rested against the firewall.(make sure to check the Y in the harness left of the ECM) to see if it has rubbed through the insulation on the firewall. Yep it shorted my ECM and was told by my local dealer that Chrysler DOES NOT make them any longer and would take 6 months to get one. found a used one reflashed it to my security and keys and it lasted 1 yr. Then all hell broke loose causing the the skim module,cluster and ECM to short out, no com out of anything, After a trip to the dealer with a new skim,cluster,keys and ECM (yes a NEW ECM from Chrysler) was installed she was alive again. With a rebuilt 4.0 and 220,000 (5500 miles on the rebuild) it runs like a new one. What cost me $500 4yrs. ago ended up around $6500 "Buy a Jeep they said"

  34. Avataaar/Circle Created with python_avatars Antonio Claudio Michael says:

    Very intriguing

  35. Avataaar/Circle Created with python_avatars DisgruntledEmployee says:

    It's a Jeep thing you wouldn't understand

  36. Avataaar/Circle Created with python_avatars 10100rsn says:

    That looks like a JTEC style PCM and the symptoms you describe are very common on those. Wriggle the connector or the wires and random things will happen… sometimes… but the engine will stutter or stall. If its got the two t-15 torx screws in the front under those connectors, remove the left one and see if it starts and runs. If so, add two washers and some loctite to the screw before screwing it back in and it should be good to go. If its the newer model with the screws around the perimeter then check each one by one or loosen them all a bit and see if it runs… Screws that are too long apparently don't know how to "Dodge" circuit boards. 😉

    Edit: I'm pretty sure the newer ones like the one in the 2005 Neon are not affected by this…

  37. Avataaar/Circle Created with python_avatars Duncan Mac says:

    Thanks for the video.

  38. Avataaar/Circle Created with python_avatars witnesszer0 says:

    i had a lot of problems on my 96 jeep gc and a lot of times it was the pcm from blowing up coils after shifting out of park to blowing up transmissions they have voltage regulator on the front thin panel that gets hot and over time bulges the front panel of the pcm

  39. Avataaar/Circle Created with python_avatars Craig Cundiff says:

    fortunately an ECM isn't very expensive….$100 at PULL A PART…. do it to it..👈

  40. Avataaar/Circle Created with python_avatars JBI AUTOMOTIVE says:

    i would gladly pay to have eric and keith teach an online class/ video tutorial on pci data bus, can network, no com

  41. Avataaar/Circle Created with python_avatars mike fedele says:

    Green goblin 👺 inside….. Bless the roadways with salt and brine.

  42. Avataaar/Circle Created with python_avatars Billy Yoder says:

    Thank you Eric. Good job. I appreciate your videos. Have a good night and weekend.

  43. Avataaar/Circle Created with python_avatars Victor R says:

    Greatness knows no rest. Good job Eric!

  44. Avataaar/Circle Created with python_avatars Jflux69 says:

    I thought the snap on broke.

  45. Avataaar/Circle Created with python_avatars Pete Medina says:

    Very interesting, he tried to save money by going used which is always a gamble on electrical parts now it's going to cost him more😞😞

  46. Avataaar/Circle Created with python_avatars Jerry Bungard says:

    Worked on a new Pontiac that had a dead pcm and replacement lasted about two seconds….had a rodent chewed spark plug wire and was blasting 40,000 volts into the wiring harness…..

  47. Avataaar/Circle Created with python_avatars GENERAL John says:

    Lol a real mechanics money maker there. Had one been there done it. Chrysler is a joke! Their vehicles are the absolute worst. I'd rather have a Range Rover.

  48. Avataaar/Circle Created with python_avatars Glycerin says:

    i clicked subscribe long ago

  49. Avataaar/Circle Created with python_avatars Martin Short says:

    As always, Great Video, learn so much watching your uploads!

  50. Avataaar/Circle Created with python_avatars Crispr Talk says:

    a southern used PCM"…. everything in the south is Better!

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