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got a code 12

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BlueOx, Oct 25, 2002.

  1. BlueOx

    BlueOx 1/2 ton status

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    OK so put on the TBI system, but now I’m having a problem. I drove the truck around yesterday and it started bucking upon acceleration. The truck idles fine but when I take off and hit the gas it just sputters. The truck felt like it had no power. When I pulled the trouble codes by jumping the aldl terminal I found a code of 12. Code 12 showed to be something dealing with the distributor spark to the computer. I checked all the wires dealing with the distributor the only thing I have not checked is the timing due to my timing light being broken. I added the VSS from the computer to the existing wire for the cruise control. I’m beginning to think the cruise control wire is not the right one. Does the VSS have anything to do with this?

    Thanks,
    Charles
     
  2. MA87K5

    MA87K5 1/2 ton status

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    A code 12 just means that you accessed the computer. Check you fuel filter. The does the same thing when it is clogged. Runs fine at idle then runs sluggish when you give it gas. Hope this helps.
     
  3. BurbinOR

    BurbinOR 3/4 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    I added the VSS from the computer to the existing wire for the cruise control. I’m beginning to think the cruise control wire is not the right one. Does the VSS have anything to do with this?


    [/ QUOTE ]

    Don't think so.........the VSS pulse generator has two wires (forget the colors) that have corresponding hookups in the wiring harness...............you have to have an actual VSS generator feeding the computer the info, the cruise control will not work. www.jagsthatrun.com is but one source of VSS pulse generators. /forums/images/graemlins/laugh.gif
     
  4. Stylzz

    Stylzz Registered Member

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    It should show a code 12 first then give you the trouble code and then show a code 12 again. Its just to let you know the computer is working.
     
  5. BurbinOR

    BurbinOR 3/4 ton status

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    By the way, I'd recommend you get a scanner or something like WinALDL to read the computer info - very valuable info even if it is not throwing codes. Helps out on drivability problems, etc. I have an AutoXray ( www.autoxray.com ), available at Shucks/Kragen/Checker stores or others.

    Jumping the terminals on the ALDL is fine for code reading only, the scanner can tell you much more. /forums/images/graemlins/thumb.gif
     
  6. TopOff

    TopOff 1/2 ton status

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    Is the computer setup for computer controlled distributor?

    Or a regular mechanical advance weight distributor?
     
  7. Burbinator

    Burbinator 1/2 ton status

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    As the others have stated, a code 12 is a handshake code. It also signals no distributor reference pulses, which stands to reason if the engine is off.

    I would check two things:
    1) Ensure the distributor is the computer controlled variety, not vacuum advance.
    2) Check the fuel system, specifically the pressure and regulator. I put an adjustable regulator on my truck with great success.

    Good luck and let us know what you find...


    /forums/images/graemlins/burb.gif
     

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