Automatic Transmission Shift Lock Control Description

Description
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 consist of the following components:
- The automatic transmission shift lock control switch.
- The automatic transmission shift lock control actuator.
- The PARK relay.
- The body control module (PZM).
With the ignition in the ON position the powertrain control module (PCM) sends a class II message to the body control module (PZM) indicating the transmission gear position. With the transmission in the PARK position the body control module (PZM) supplies a ground to the PARK relay control circuit. This energizes the PARK relay coil and closes the switch contacts. With the contacts closed voltage is supplied through the normally closed contacts of the automatic transmission shift lock control switch to the automatic transmission shift lock control actuator. The permanently grounded automatic transmission shift lock control actuator energizes mechanically locking the transmission shift lever in the park position. When the driver presses the brake pedal the contacts in the automatic transmission shift lock control switch open de-energizing the automatic transmission shift lock control actuator. This allows the shift lever to be moved out of the PARK position.