Automatic Transmission Shift Lock Control System

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 transmission control module (TCM)

The BCM controls the ground circuit of the shift lock control solenoid. The following conditions must be met before the BCM will supply a ground to the shift lock control solenoid:

• The ignition is in the ON position.
• The TCM sends a class 2 message to the BCM indicating the transmission is in the PARK position.
• The BCM receives a brake applied input from the stop lamp switch.

The shift lock control solenoid is supplied battery voltage from the Ignition 1 fuse. When the BCM supplies a ground to the control circuit of the automatic transmission shift lock control solenoid, the solenoid energizes, releasing the mechanical lock. 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 switches the ground of the shift lock control solenoid OFF, de-energizing the shift lock control solenoid. The de-energized solenoid mechanically locks the shift lever in the PARK position.

Vehicles equipped with continuously variable transmission (CVT) in cold weather temperatures below -25 degrees C (-13 degrees F) the ECM will send a class 2 message to the BCM preventing the operation of the shift lock control solenoid and the temperature gage will flash. Once the transmission has warmed above -25 degrees C (-13 degrees F) the temperature gage light will stop flashing and normal shift lock control operation will resume.