Automatic Transmission Shift Lock Control Description and Operation

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

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 thew following components:

The automatic transmission shift lock control solenoid
The body control module (BCM)
The powertrain control module (PCM)

With the ignition in the ON position, the BCM directly monitors the brake switch input and receives a class 2 message from powertrain control module (PCM) indicating the automatic transmission gear position. With the ignition ON, brake pedal released and the transmission in the PARK position the BCM supplies battery voltage to the shift lock control solenoid. The shift lock control solenoid is permanently ground, therefore energizes mechanically locking the shift lever in the PARK position. When the driver depresses the brake pedal the BCM receives a brake switch input and turns the control voltage output of the shift lock control solenoid OFF. This de-energizes the shift lock control solenoid, allowing the driver to move the shift lever out of the PARK position. When the transmission is out of the PARK position the shift lock control solenoid remains de-energized.

During remote start operation the BCM will energize the shift lock control circuit, locking the shift lever in the PARK position.