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 transmission control module (TCM) |
The BCM controls the voltage to the shift lock control solenoid through the shift lock control solenoid controlled voltage circuit. The following conditions must be met before the BCM will supply voltage to the shift lock control solenoid:
| • | The ignition is in the ON position. |
| • | The engine control module (ECM) sends a GMLAN serial data message to the BCM indicating the transmission is in the PARK position via the TCM. |
| • | The BCM determines the brake pedal is applied according to the brake pedal position (BPP) sensor. |
Since the shift lock control solenoid is permanently grounded, the BCM supplies voltage to the automatic transmission shift lock control solenoid, releasing the mechanical lock on the shift lever as the solenoid energizes. The energized solenoid allows the driver to move the shift lever out of the PARK position. When the brake pedal is not applied, the BCM turns the control voltage output of the shift lock control solenoid OFF, de-energizing the shift lock control solenoid. When the transmission is in the PARK position, the de-energized shift lock control solenoid will prevent shifting as the lever is mechanically locked in the PARK position.
