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Thread: PCM refuses to deliver spark

  1. #1
    Tuner in Training bson's Avatar
    Join Date
    Aug 2016
    Location
    Taby, Sweden
    Posts
    24

    PCM refuses to deliver spark

    Hi,
    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
    Tuner
    Join Date
    Aug 2016
    Location
    swansea south wales UK
    Posts
    102
    Sounds like an earth issue on the engine or in the loom possibly even the PCM itself
    Gen3 LM7/4L60E LS3 cast manifolds, Small Cam change, 2800 Convertor, MPVI, using MTX-L for wideband tuning