GM Service Manual Online
For 1990-2009 cars only

Circuit Description

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

    • EEPROM Checksum
    • ROM Checksum
    • RAM Checksum
    • RAM Malfunction

Conditions for Setting the DTC

    • Critical operational parameters stored in EEPROM have failed checksum test indicating invalid data.
    • Masked ROM code has failed checksum test indicating that masked ROM data is no longer valid.
    • ROM code has failed checksum test indicating that ROM data is no longer valid.
    • One or more RAM locations have failed operational test indicating that some portions of RAM are not functional.
    • 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

  1. Replace the transfer case shift control module.
  2. Perform the transfer case shift control module.