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Thread: 4l80e shift problems, bad segment swap or bad pcm

  1. #1

    4l80e shift problems, bad segment swap or bad pcm

    Bought the truck with the swap already done, every thing was fine. Swapped in a pcm I already had licensed, done my segment swap and now it has trouble down shifting from 3rd to second. Re done the segment swap and still has problems. also relocated the battery during the pcm swap, so it could possibly be a ground problem (every thing els works so I doubt it)

    Brough out the volt meter, and with hpt. Scanner I can command 2nd (both solenoids off) I still have ground to both solenoids even at the pcm with 2 short leads off the pins (pulled the 2 wires that go to the trans and put 2 pins in with only 3" of wire so it's not a a short in the trans harness side)

    Here are my results wile commanding different gears and there readings

    Switch to command 1st (A on, B off) I have 11.9v at A and 10.8v at B.

    Command 3rd (A off, B on) I have 10.8v at A and 11.9v at B.

    command 4th (both A and B on) I have 11.9v at both.

    from my understanding, pcm switches ground when the pcm commands a solenoid on, so there for if the solenoid is commanded off, it shouldn't be grounded so I shouldn't have any ground from the pcm when the solenoid is commanded off correct?

  2. #2
    swapped in a different pcm and its still has ground at pins 47 and 48.

  3. #3
    Turns out I was the pcm. Pins 47 and 48 are grounded when disconnected from the solenoid, not sure why but they are. With all the pins plugged in, I put the voltage gauge on the b solenoid wire (pin 47) and when commanded to kill the ground, it would take 10-15 seconds to slowly taper off. Swapped back to stock 4l60e segment and still done it. Swapped in new computer, licensed it, segment swapped and all works like it should now.