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Thread: Another TCC no lock issue

  1. #1
    Potential Tuner
    Join Date
    Sep 2020

    Another TCC no lock issue

    Hello all
    I have a 4l60 and TCC will not lock up.
    Troubleshooting that has been done.
    1:Brake switch verified good suppling 12v to ecm pin 33 blue connector. Push brake 0volts.
    2:Misfires maxed out
    3:gear ratio/tire size corrected.
    4uty cycle 100/90 also tried 100/99
    I can command TCC to engage using scanner and TCC does engage.( I can feel the RPM drop big time )
    When I take the car for a drive and scan, TCC mode will go from off to apply to apply en then locked but there is no RPM drop at all.
    So I splice a wire at ECM red plug terminal 42 and put my test light on that wire and took another drive.
    when the scanner says the TCC mode is locked my test light does not light up telling me that the ECM did not provide a ground. I tried this several times and no light when TCC mode says locked..
    I then command the TCC to lock via scanner and yes my light came on telling me that when I command the ECM to lock TCC it provides ground on PIN 42..
    Conclusion: Has anybody had a bad ECM cause this issue? Is it possible that the ECM is bad?
    I'm pulling my hair out trying to figure this out. I find it weird that I can command TCC lockup with scanner but it doesnt lock when TCC mode says locked.
    On a side note I notice that when the TCC goes from apply enable to apply the TCC apply time counter always counts up to 6.4 sec.
    Sorry for writing a novel
    any advice will be greatly appreciated I am very new to this but I did read a lot before posting
    Thank You
    Attached Files Attached Files

  2. #2
    Potential Tuner
    Join Date
    Sep 2020
    Anybody have any input ?

  3. #3
    Senior Tuner Lakegoat's Avatar
    Join Date
    Jul 2012
    I had this exact problem when I switched from a manual trans to an auto. Had to send the computer out to have an auto os installed with the right GM system. E40 and T42 plus they had to be paired?
    2005 GTO, TrickFlow 225, Magnuson 2300, 4L80, 4 link 8.8
    2013 Silverado 5.3, 6L80