GM Service Manual Online
For 1990-2009 cars only

The automatic transmission shift lock control system is a safety device that prevents an inadvertent shift out of PARK when the engine is running. The driver must press the brake pedal before moving the shift lever out of the PARK position. The system consists of the following components:

    • The automatic transmission shift lock control solenoid
    • The remote control door lock receiver (RCDLR)
    • The transmission control module (TCM)

With the ignition in the ON position, battery positive voltage is supplied to the automatic transmission shift lock control solenoid located within the shift lever assembly. The automatic transmission shift lock control solenoid receives a ground from the RCDLR. The RCDLR receives input thought data communications from the TCM indicating transmission gear position and brake pedal position. With the shift lever in the PARK position the internal park switch of the shift lever assembly closes allowing current to flow to the RCDLR. When the RCDLR receives a data communication that the brake pedal is depressed and the transmission is in the PARK position the RCDLR supplies a ground the shift lock control solenoid control circuit. This energizes the solenoid and allows the shift lever to be moved out of the PARK position. With the shift lever out of the PARK position the internal park switch in the shift lever assemble opens, this de-energies the shift lock control solenoid.