Automatic Transmission Shift Lock Control Description and Operation

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

• The automatic transmission shift lock control solenoid, is located within the automatic transmission shift lever.
• The Body Control Module, which controls the voltage supply circuit of the park lock control solenoid.
• The Engine Control Module.

The Body Control Module controls the voltage to the automatic transmission shift lock control solenoid through the shift lock control solenoid controlled voltage circuit. The following conditions must be met before the Body Control Module will supply voltage to the automatic transmission shift lock control solenoid.

• The ignition is in the ON position.
• The engine control module sends an input via serial data to the body control module indicating the transmission is in the PARK position.
• The Body Control Module receives a brake applied input from the Stop Lamp Switch.

Since the shift lock control solenoid is permanently grounded, the Body Control Module 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 Body Control Module 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. During remote start operation the Body Control Module will de-energize the automatic transmission shift lock control circuit, locking the shift lever in the PARK position.