Check Engine light on 2001 GMC 8500 goes on under load

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Billariss, Jul 11, 2020.

  1. Billariss

    Billariss Bobtail Member

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    Jul 11, 2020
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    My truck with Cat 3126 when its under load some time the check engine light comes on and the truck goes into limp mode. Shut the truck off and restart and then its fine for a bit then does the same thing. No codes coming up. fuel fitters have been changed
     
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  3. Goodysnap

    Goodysnap Road Train Member

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    The ecm is turning the light on for sure. What are you using to read codes?

    Find someone with ET to get hooked up.
     
    AModelCat Thanks this.
  4. AModelCat

    AModelCat Road Train Member

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    If there's a light, there's a code. CAT ET will pull all the active and inactive faults and events. CAT ECMs typically will only record up to 255 events of a fault before it stops counting, so you may need to clear all the logged faults and go for a drive to pinpoint the code that's throwing the light on.
     
  5. Billariss

    Billariss Bobtail Member

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    Jul 11, 2020
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    Sorry the shop I took it to told me the one they has wouldn’t link up they tried on a different truck and it did. We also tried with the cruse control and we couldn’t get it to come up ether
     
  6. Goodysnap

    Goodysnap Road Train Member

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    Your gonna have to find somebody that can hook up. Either fix the communication issue on the truck side or have a CAT guy hook up direct to the ECM.
     
    BoxCarKidd and spsauerland Thank this.
  7. Billariss

    Billariss Bobtail Member

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    Jul 11, 2020
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    Took it to a cat dealer and it was the IAP Control valve all seem to be good now thanks for the help
     
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