jeep cherokee -02 3.7 immobilizer problem?

Discussion in 'KJ General Discussion' started by cleaf, May 31, 2019.

  1. cleaf

    cleaf New Member

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    hi

    car will crank but wont start, it keeps blowing fuse 34 (radio etc..), i have disconnected radio and fuse doest blow so radio is broken.

    immobilizer light wont turn off on the dash so can radio can have something to do with immobilizer, it has that immobilizer blinking light on it.

    it did also blow fuel pump fuse but problem was faulty relay.

    [​IMG]
     
  2. Billwill

    Billwill Full Access Member

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    Immobilizer light blinking means that the PCM has received the SKIM code from the SKIM module that sits at the top of the steering column but is not happy with the code. Usually the Jeep will turn over and fire up but will cut out after about 20 seconds.

    Just to confirm...is the light flashing all the time or is the light ON all the time?

    This SKIM code is read from the chip inside the ignition key by the SKIM module that has a loop of wire going around the key entrance.
    The chipped key, the SKIM module and the PCM must all have the same code programmed inside themselves.

    Have you tried a different Chipped Key?

    Try re-plugging the connector on the SKIM module at the top of the steering column behind the plastic covers and re-plug the PCM connectors in case you have bad connections.

    Otherwise you may have a wiring issue.

    When the PCM is happy with the code received it energizes the ASD Relay so maybe swap that over but if the ASD Relay does not send acknowledgement back to the PCM that it...the ASD Relay..has energized then the SKIM light stays ON without flashing. The Jeep will turn over but not fire.
    I had this above problem on my 2002 Export CRD caused by a broken wire going to one of the ASD relay coil connections stopping the relay from energizing.
    I could jumper out pins 30 and 87 inside the ASD relay and get the Jeep going until I was able to track down the broken wire.
    This is not a way of Hot-wiring the Jeep....if the PCM does not receive the correct code from the key it will stop the Jeep from firing up!

    So if your light is ON all the time...engine turns over but does not fire then you can try jumper pins 30 and 87 together inside the empty female socket...if it now fires and runs you need to trace the wiring to see if the ASD relay is energizing and if the PCM is receiving this information. Fuse #16 and fuse #26 under the hood are the first things to check....jumping pins 30 and 87 together will not work if these fuses are blown!

    According to the Service Manual the SKIM module can only be programmed once ie. a brand new SKIM module would need to be fitted and programmed by the Dealers. You could pick up a set of chipped keys, SKIM module and PCM from the same scrapped Jeep at a Breakers yard and fit all three together in your Jeep.

    Do you have the 2002 Jeep KJ Service Manual download?
    This document gives you the Theory of Operations of how the SKIM system works and section 8W has the wiring diagrams.

    www.colorado4wheel.com/manuals/Jeep/KJ
     
    Last edited: May 31, 2019
  3. cleaf

    cleaf New Member

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    ok some progress.

    no spark.
    Tried to unplug and replug SKIM, nothing happened light still comes on. And i have only one key to car.
    ASD relay wont operate, if you put ground from straight from battery it will operate. In pin 30 comes 12V.
    Tried to jump pins 30 and 87 but it didnt start and checked also fuses 16 and 26 they were ok but i did change them anyway.

    so that skim module is broken?
    can you bypass that somehow? or is the dealer only way to fix this problem?

    and thank you for great reply!
     
  4. Billwill

    Billwill Full Access Member

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    OK so does the light stay on permanently...not flashing?

    Does engine turn over but not fire?

    If so then either your chipped key is faulty and you need to take it to the Dealers with proof of ownership of the Jeep for them to supply you with new ones or you have most likely a wiring problem.

    If you look at the wiring diagrams for the ASD relay you should be able to see if it is energizing as it should if the chipped key has been recognised by the PCM. In other words both +12 volts and ground must be present on the coil of the ASD relay.

    If there is +12 volts on pin 30 (red/yellow) then you need to trace if the wire coming off pin 87 (dark green/orange)is finding its way to the correct pin at the PCM at the PCM...ie. wire not broken, not shorting to ground, not a bad connector in its path and not a dirty pin at the PCM connector....you should be able to find +12 volts right at the wire before it enters the PCM connector.

    Wrap a sharp pin or needle around the Red lead of your multi meter and pierce the insulation in the wire just before it enters the PCM to contact the copper wire within...you can seal the insulation afterwards with some glue or melting the insulation with a soldering iron.

    If that +12 volts is present there then possibly the PCM or that connector is faulty but as I stated the Jeep cannot be Hot Wired by placing +12 volts there....the PCM has other secret means of stopping the Jeep from firing.

    I would start by getting the Dealers to provide you with new programmed keys and if that does not work then the Dealers will need to check out the PCM and SKIM/SKREEM module on top of the steering column....the PCM/ECM is usually a pretty robust component.:(

    What year/model is your Jeep...presume it is 2002 3.7 gasser.

    I will look through the wiring diagrams...used to be able to post copies of scanned-in pages from my PC from my Laptop but not sure about that on this revised new site look!

    Edit to Add: I am used to the SKIS system on the Diesel models...looking through the wiring diagrams it would seem that the Gassers may work differently as regards the use of the ASD relay. So I need to know if lamp is flashing or is ON solid or flashing so that I can go through the wiring diagrams!

    Fuses of interest are Fuse #36 30 A and Fuse #26 15 A in PDC ie. box under the hood.
     
    Last edited: Jun 9, 2019
  5. cleaf

    cleaf New Member

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    Yes engine will turn over but wont start.

    I measured pin 30 and it shows +12V so thats ok, mayby i try to check that pin 87 wiring is that ok.

    model is 2002 cherokee 3.7

    Immobilizer light comes on when you turn key, turns off for a second and comes back on without blinking.

    Can you check somehow is that SKIM module broken?

    But i think best to do at this point is get new key and try with that...

    And i will check those fuses 36 and 26 are they ok.
     
  6. Billwill

    Billwill Full Access Member

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    OK check fuses #15 and #33 under the hood.

    The Sentry Key Immobiliser Module....which I presume is the SKIM module at top of steering column has 5 pins...if the wire colors do not match up then we are in the wrong movie!

    With ignition ON check the following:

    Pin #1 Pink/Red stripe Fused B+ 12 volts from fuse #33
    Pin #2 Black/White stripe Ground G202
    Pin #4 Black/Tan stripe likewise Ground G202
    Pin #3 Dark Blue +12 volts Run/Start from fuse #15...turn key to Start for this reading.
    Pin #5 Yellow/Violet/Black PCI Bus

    Pin #5 PCI Bus is very hard to trace as the PCI bus is a serial bus that runs all over the place to all the modules from the Cluster to the PCM etc. A short or break anywhere on this line holds everything up.

    The early KJs used only the PCI bus which most Code Readers cannot read....later KJs use Mainly CAN, SCSI and some PCI Busses.

    All this above is from Wiring Diagram 8Wa-39-6

    The wiring diagrams will show where ground point G202 is located.
     
    Last edited: Jun 11, 2019
  7. cleaf

    cleaf New Member

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    ok il check SKIM too.

    Does radio have something to do with this fault?

    It all began when radio started to burn fuse???
     
  8. Billwill

    Billwill Full Access Member

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    Yeah I agree that fault is probably related to the radio blowing fuses so there may be more fuses blown. Fuses may look OK but there may be dirty contacts..best to check with a meter if you have +12 volts on one side of the fuse then +12 volts should be on the other side of the fuse. Also pull fuses out...measure with Ohm-meter and re-insert...this usually cleans up the contacts.

    The radio also is usually connected to the PCI Bus..depends on the type of radio you have. The PCI Bus is what I am concerned about as it is what the SKIM Module uses to communicate with the PCM but if you have completely dis-connected the radio then it should have no effect on the PCI Bus but check the cabling in that area around the radio.