Question about 2002 Jeep Grand Cherokee

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Where is the ecm chip located on a 2002 grand cherokee

I replaced the fan relay and the engine light stayed on and the fan still dosent work

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  • jason messinger Feb 16, 2012

    the code is p1491 autozone cheked it and the printout says 3 probable causes open or shorted fan relay,open or shorted circut condition,ecm defective

  • ZJ Limited
    ZJ Limited Feb 16, 2012

    P1491 is for the cooling fan relay control circuit as you've found already.
    Start by checking the fuse for the fan relay. Its in the box under the hood, a 40 amp fuse.
    - If you've got a couple jumper wires, you can unplug the fan connector and carefully jump the fan to see if it works. The fan connector is on the right side of the back of the fan shroud. Unplug it and jump the black wire to ground and the green to positive. You've got to be very careful doing this though-you are in very tight quarters, its not hard for your jumper wires to touch each other in the connector and short together, and if you use small diameter jumper wires they will get hot quickly when the fan comes on.
    - If the fan doesn't come on when you jump it, or if it runs slow or sounds bad, you've got a bad motor and will need to replace the fan assembly. One thing that does happen somewhat often, is a bad fan motor will burn up the relay. If the fan motor is drawing too much current it will overload the relay and burn it up. This is why its so important that if the fan motor runs slow or makes noise that you replace it, or you may end up burning up relays frequently.
    - If the fan runs and the fuse is good, its very likely you just need a fan relay. This is a pulse width modulated relay, not the on/off clicker type you'd find in the fuse box. This unit is capable of infinite speed control. It gets very hot in operation, so its mounted to the body sheet metal to allow heat to dissipate through the sheet metal. The relay is mounted under the right headlamp held down with two 8mm screws. To get to it you have to remove the front bumper cover and headlamp bracketry to access the relay. These relays are pretty common.

  • ZJ Limited
    ZJ Limited Feb 16, 2012

    Jason, also could visit this link:
    Good luck.



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  • Jeep Master
  • 17,970 Answers

If engine light stay ON, I suggest scanned the PCM to know ecaxtly what fault code is stored there, this code number could be related with fan malfunction.

If you dont have a OBD scanner reader, just turn the key at ON (dont start engine) three times, On-Off-On-Off-On and read odometer as Pxxxx codes, note this and come back again with this information.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Posted on Feb 16, 2012

  • 4 more comments 
  • jason messinger Feb 16, 2012

    the code is p1491 autozone cheked it and the printout says 3 probable causes open or shorted fan relay,open or shorted circut condition,ecm defective

  • jason messinger Feb 21, 2012

    i jumped the fan and it still works the fan relay was replaced when the engine light came on . is it the ecm chip?

  • ZJ Limited
    ZJ Limited Feb 22, 2012

    You are right, if two first possible causes are solve it or tested, your las choice could be ECM go to bad; try to testing with other ECM, under this condition, if the "light" dont come on again, will need look some ECM in junkyard according with your year and model.

  • jason messinger Feb 23, 2012

    where is the ecm located?

  • ZJ Limited
    ZJ Limited Feb 23, 2012

    ECM = PCM (Poertrain Control Module); check in he follow link the module locations diagram:

    1. BCM - Body Control Module
    2. PDM - Passenger Door Module
    3. AM - Airbag Control Module
    4. MIC - Mechanical Instrument Cluster
    5. EVIC - Electronic Vehicle Information Center
    6. CAB - Controller Antilock Brakes
    7. TCM - Transmission Control Module
    8. SKIM - Sentry Key Immobilizer Module
    9. HSM - Heated Seat Module
    10. MHSM - Memory Heated Seat Module
    11. DDN - Driver Door Module
    12. PCM - Powertrain Control Module
    13. SM - Sunroof Module
    14. RSM - Rain Sense Module
    15. APM - Adjustable Pedals Module

    Good luck.

  • ZJ Limited
    ZJ Limited Feb 23, 2012

    Check engine bay, firewall passenger side.



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SOURCE: where is the fan relay located and what makes it

Under the hood in a black box on the drivers side or passingers side look for alot of wires going in it.

The part Chrysler supplied came with an incorrect diagram and instructions. The note said the "LEFT" headlight and the diagram illustrated this along with a note to remove the air snorkel. Your answer was the correct direction. It is the left headlight as you FACE the car. The headlight was removed by taking out the 10mm stem nut and gently using a pry bar, outside edge first, then inside edge. Trying to remove the headlight rapidly will result in a broken plastic tab that will need to be epoxied.I used my 2" hole saw to create an access by cutting through the headlamp plastic cavity behind the headlight, a strong light will reflect onto the relay and you can see the bracket part below and between the battery and front frame toward the front of the car. With the headlight assembly out, I prised the white ball socket fittings and oiled them for ease of refit. The piece of the cavity was saved because it is critical to keep water out of the relay area. There is a small red tab on the connector of the relay that needs to be pressed and the red tab moved to the side. Then insert a screwdriver into the bottom of the connector to release the black plastic tab that locks the connectors together. Hold the new relay in your hand. Push the red tab back across the connector body and push the two halves together, they will now lock It is critical that a good flat install be performed or the part will fail and you're out $75 and the time to redo it all over again. Use the new screws in the part bag, the old ones will not tighten enough for a good grounding of the part. I used metal duct tape to tape the plastic piece back into the hole and then sealed it with two more pieces. Pressing the headlight assembly back works best if you start from the outer edge and then press the bottom edge in.

Also, I suggest review the Service Manual for WJ Grand Cherokee.

Good luck.

Posted on Oct 13, 2009

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