2004 Allison HD truck check engine light

Discussion in 'GMC Truck Forum' started by gmctrucks, Oct 25, 2016.

  1. gmctrucks

    gmctrucks Full Member

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    Ok guys my brothers 2004 HD truck was coming up with a check engine light every day so him and I did some research and what was coming up on the scanner was the TCM was losing communication to the ECM well some months ago he had his radiator changed out and the plug to the TCM wasn't connected in correct so what my brother seen or felt when he unplugged the TCM that it felt kinda loose so he looked at it more closely and he noticed that the rubber seal to the plug was folded wrong when plugging it in so he took a small screwdriver and he fixed the rubber seal right so it could make a good connection so that was the problem its running like a champ no more check engine light now the ECM are both located inbetween the fan and battery on the driver side... the TCM is bolted to the fan scroud and the ECM is right below it off the frame.
     
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  2. dirtrider73068

    dirtrider73068 Moderator
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    Once a code is set its stored in memory till cleared. ECM stays in a default mode untill code is cleared once the issues is fixed. Once code is cleared ECM reverts back to OEM programming. If haven't yet need to clear the code see if the issue is fixed. If not code will return.
     
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  3. gmctrucks

    gmctrucks Full Member

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    True that he did that do its all good now and it was such a easy fix instead of a Trans shop or dealership wanting to charge you a arm and a leg so all in all I hope this might help some members here.
     
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  4. MrMarty51

    MrMarty51 Full Member

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    Good works there GMC. Always a good feeling when the problem gets solved, and so easily too.
    Thank You for posting this to the forum.
     
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