Service Soon digital dash Out
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HT4100 4.1, 4.5, 4.9 Discussion, Service Soon digital dash Out in Cadillac Engine Technical Discussion; I have an 86 coupe deville which i accidentally Jumpstarted with the terminals reversed. It blew fuses in both fuse ...
  1. #1
    Crackillac's Avatar
    Crackillac is offline Cadillac Owners Member
    Automobile(s): 86 Coupe DeVille
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    Mar 2009
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    Shreveport, LA
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    Service Soon digital dash Out

    I have an 86 coupe deville which i accidentally
    Jumpstarted with the terminals reversed. It blew fuses in both fuse blocks which i replaced. The car runs fine but none of the digital
    Dash lights will come on. The radio plays but no time or station display. No speedo or mpg display. The Service Soon light is on. Is this something they can check at autozone with a computer device or have i blown up or melted down some computer board?

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  3. #2
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
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    Re: Service Soon digital dash Out

    I think you shorted the BCM (Body control module) You have a code reader in your car already. AutoZone wont be able to help.

  4. #3
    Crackillac's Avatar
    Crackillac is offline Cadillac Owners Member
    Automobile(s): 86 Coupe DeVille
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    Shreveport, LA
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    Took me a while to get around to this project but i pulled the bcm today and im no expert with circuitry but i don't think these little things are supposed to be melted together like they are.. Or maybe im wrong, i really don't know what I'm looking at lol



    image-474393682.jpg

  5. #4
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
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    Re: Service Soon digital dash Out

    I would think any computer repair shop should be able to tell you by looking. There is also a "constant power supply module" located just above the gas pedal that can be shorted out. About the size of a pack of cigarettes, silver. Its held vertical with 2 8 MM ? nuts on a bracket. You can remove the nuts and it will drop down and dangle by the harness plugged into it. It will say CONSTANT POWER SUPPLY on its white label. I damaged one of those by hooking up an aftermarket stereo once and digital dash display went blank. You'll find them on 86 thru 89's I believe.

  6. #5
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
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    Location
    california
    Age
    67
    Posts
    5,783

    Re: Service Soon digital dash Out

    Disregard the mention of the constant power supply! Got my models mixed up. Eldos and Sevilles had them, not coupes and Sedan DeVilles. .

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