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Thread: diagnose this

  1. #1
    Join Date
    Mar 2008

    diagnose this

    I have an older Gmc van 1989 3500 with a 5.7 engine automatic trans
    we get the error code 42, four flashes then two flashes. the books I have describe this but do not say how to correct th problem.
    very poor gas millage and throttle response.

    While setting the timing at zero degrees with the wire disconnected from the distributor. at reconnection of this wire the computer retards the timing up to 20 degrees.

    Thanks for your help Jay

  2. #2
    Neither darque nor pervert DarquePervert's Avatar
    Join Date
    Apr 2004
    Moved to off topic.
    Understand that these foprums are focussed on vehicle PCs. Most of us aren't mechanics that can troubleshoot engine trouble codes.
    Have you looked in the FAQ yet?
    How about the Wiki?

    Under normal circumstances, a signature would go here.

  3. #3
    Maximum Bitrate fixerofallthing's Avatar
    Join Date
    May 2005
    Lawrenceville GA

    1. Disconnect the set timing connector or ground the Tan/Black bypass wire.

    2. The check engine light should come on and code 42 should set.

    3. If the engine stops stalling, disconnect the pick up coil connector at the Ignition Control Module (ICM).

    4. Check acv output from the pick up coil while cranking the engine at a normal cranking speed.

    5. If output is less than 700 mv replace the distributor shaft with a new one.

    6. If the engine still stalls with the bypass open or shorted to ground see if adding alternative fuel to the throttle body helps.

    7. Wet down the coil and coil wire with water and see if the stall is induced at a higher RPM.

    8. Check for a loss of injector pulse or spark.
    Potential Causes:
    Distributor shaft
    Coil wire

    ** Confirmed Fix **
    The Car 2005 Scion xB

    The Truck 2004 GMC Canyon

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