Shift Interlock: Description and Operation

Automatic Transmission Shift Lock Control Description and Operation

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 body control module (BCM)
* The powertrain control module (PCM) if equipped with the 3.6L engine
* The transmission control module (TCM) if equipped with the 3.8L engine

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 solenoid.

* The ignition is in the ON position.
* The PCM sends an input to the BCM indicating the transmission is in the PARK position if equipped with the 3.6L engine.
* The TCM sends an input via Class 2 serial data to the BCM indicating the transmission is in the PARK position if equipped with the 3.8L engine.
* The BCM determines the brake pedal is not applied according the brake pedal position.

Since the shift lock control solenoid is permanently grounded, the BCM supplies voltage to the automatic transmission shift lock control solenoid, mechanically locking the shift lever in the PARK position as the solenoid energizes. When the brake pedal is applied, the BCM turns the control voltage output of the shift lock control solenoid OFF, de-energizing the shift lock control solenoid. The de-energized solenoid releases the mechanical lock 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.