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Thread: PCM refuses to deliver spark

  1. #1
    Tuner in Training bson's Avatar
    Join Date
    Aug 2016
    Taby, Sweden

    PCM refuses to deliver spark

    I am currently having a problem with no spark and no injector pulses on my LS1 -99. Here are some facts and background:

    - One day recently it simply refused to start.
    - The car is a Chevy Business Coupe -40 with 5.7L LS1 -99 and 4L60E.
    - Wiring harness is PSI HAR-1016.
    - VATS are disabled.
    - It has been running fine for years and no modifications made lately.
    - The battery is fresh and it is cranking as it should.
    - The fuel pump is priming as it should and I have pressure in fuel rails.
    - All fuses and relays checked and are ok.
    - No spark at spark plugs while cranking!
    - No pulse signal to the injectors while cranking!
    - I have a good 12V from the ignition relay at the fuse/relay center of the harness.
    - The HP tuner communicates fine with PCM and I can read the tune and scan for error codes.
    - The codes I get from scanning is P0102, P0203 (I'm running in SD mode without MAF sensor), P1571(pending,history),P1689(ses,current).
    I have allways had these codes and I don't think these are related to the problem.
    - I verified with the HP tuner/scanner that the crank and cam sensors are giving signals as expected.

    Now I'm completely out of ideas. Any hint or suggestion on what to do is appreciated!

  2. #2
    Join Date
    Aug 2016
    Swansea Wales UK
    Sounds like an earth issue on the engine or in the loom possibly even the PCM itself
    Gen3 L59/4L60E LS3 cast manifolds, Small Cam change, 2800 Convertor, MPVI, using MTX-L for wideband tuning