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2004 GMC Envoy SLT 4.2L no spark at spark plugs boots why?

The engine will turn over but want start there is no spark can anybody tell me what could be all the causes why there is no spark at the spark plugs boots and what all i need to check? where are the fuses box located at inside the vehicle? please help me

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  • Joe Russell Dec 03, 2016

    i have a sensor tester i test the crankshajt position sensor it test out ok how i do it i connect the two wires to the sensor and crank the engine when the the lights blink on my tester that mean the sensor is good and the lights do blink. where is the Ignition Control Module located? the coils on this vehicle is over the spark plugs.

  • Joe Russell Dec 03, 2016

    i have a sensor tester i test the crankshajt position sensor it test out ok how i do it i connect the two wires to the sensor and crank the engine when the the lights blink on my tester that mean the sensor is good and the lights do blink. where is the Ignition Control Module located? the coils on this vehicle is over the spark plugs.

  • Joe Russell Dec 03, 2016

    i download the owner's manual i look through it i didn't find no troubleshooting guide to help me with my vehicle that cause no spark at the spark plugs and no stsrt what's next?

  • montehammons Dec 03, 2016

    Coil on plug, ok. Not sure if even is an ICM then. I think the ECM controls the coils on that system. I recommend you do what Yadayada says in his answer: check for fault codes. After that, if no codes, I don't know. A Haynes repair manual might give some trouble shooting for no spark.

  • Joe Russell Dec 03, 2016

    i check for codes they are P2101,P1516 these codes was read with my OB2 scan tool 3040c after the battry cable has been disconnected.

  • yadayada
    yadayada Dec 03, 2016

    The ICM is incorporated into the PCM.

  • yadayada
    yadayada Dec 03, 2016

    I suggest you have a local repair look into this

  • Joe Russell Dec 03, 2016

    what you mean the ICM is incorporated into the PCM?

  • Joe Russell Dec 04, 2016

    you said i have two fuse boxes i found one under the hood where is the one located inside?

  • yadayada
    yadayada Dec 04, 2016

    You have the info figure it out please.

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  • GMC Master
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Usually no spark is one of the following: bad ignition coils, bad ignition control module (ICM- probably located underneath the coil pack), Crank position sensor, and camshaft position sensor. Also, the computer- PCM, but this is rare.

Other things, too, but often one of the above. Now if you happen to blow a maxi-fuse, that could also cause no spark, if the fuse controlled some part of the ignition system. Good idea to check all fuses on the car, but the main ones with running the engine are the maxi-fuses under the hood. I don't think any fuses inside, like under the dash, would affect or cause a no start, no spark condition. Just check the main large fuses in the Power Distribution Box- may have a cover on it, with location and function of all the relays and fuses in that box.

Probably the first thing to check would be the Ignition Control Module. Parts stores can test these for free, if you bring it to them. Mechanics would use a voltmeter when checking electrical circuits, can't test or check much without one.

Posted on Dec 03, 2016

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  • GMC Master
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This is most likely the crankshaft sensor, It tells the ECM when to fire the plugs. The sensor is on the block visible on the drivers side through the wheel well of from under the truck

Posted on Dec 03, 2016

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