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2001 GMC 2500 HD transfer case won't shift

Discussion in 'Truck & Equipment Repair' started by OSCLandscaping, Jan 24, 2014.

  1. OSCLandscaping

    OSCLandscaping Member
    Messages: 32

    My wife was plowing and the service 4wd message appeared. She tried the 2 wd button but it wouldn't come out of 4wd. She pushed the 4 low button and it shifted into 4 low and got stuck in 4lo.

    Put a new switch in and a new encoder motor on it. Put the transfer case into 2 HI manually upon install of new encoder motor. Nothing happens now when any switch is pushed, it stays in 2hi. I am getting a code CO 308. Any suggestions.
  2. Plowtoy

    Plowtoy Senior Member
    Messages: 929

    Sounds like you have replaced every thing that normally fails... The only thing left is the TCM (transfercase control module) which is under the dash above the gas pedal area if I remember correctly. Most of the time the encoder motor fixes the problems, but on rare occasions a TCM will fail. You may want to bring it in and have it properly diagnosed, and I think a new TCM will have to be programmed to the vehicle that it is being installed in anyway. Good luck!!
  3. OSCLandscaping

    OSCLandscaping Member
    Messages: 32

    Thanks for the input. The TCCM is the only other thing I can think of as well.