GM Service Manual Online
For 1990-2009 cars only

Circuit Description

At each power up the module runs a self test on the following:

    â€¢ EEPROM Checksum
    â€¢ ROM Checksum
    â€¢ RAM Checksum
    â€¢ RAM Malfunction
    â€¢ Relay Malfunction

Conditions for Setting the DTC

    â€¢ Critical operational parameters stored in EEPROM have failed checksum test indicating invalid data.
    â€¢ Masked ROM code has failed checksum test indicating that masked ROM data is no longer valid.
    â€¢ ROM code has failed checksum test indicating that ROM data is no longer valid.
    â€¢ One or more RAM locations have failed operational test indicating that some portions of RAM are not functional.
    â€¢ Motor circuit test has indicated that one of the module's relays is not able to make contact.

Action Taken When the DTC Sets

The SERVICE indicator (AWD/4WD) lamp will be latched on and the system will be disabled.

Conditions for Clearing the DTC

    â€¢ Replace the transfer case shift control module.
    â€¢ Perform the Transfer Case Diagnostic System Check.