Description & Operation: Introduction

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 switch (part of stoplamp switch).
• The automatic transmission shift interlock solenoid (may be referred to as shift interlock actuator).
• The body control module (BCM), also known as the platform zone module (PZM).
• The PARK relay.
• The powertrain control module (PCM).

With the ignition in the ON position, the PCM sends a class 2 serial data message to the PZM and the Instrument Panel Cluster (IPC) indicating the transmission gear position. With the transmission in the PARK position, the 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 from the PARK relay battery voltage circuit through the normally closed contacts of the stoplamp switch, to the automatic transmission shift interlock solenoid. The permanently grounded automatic transmission shift interlock solenoid energizes, mechanically locking the transmission shift lever in the PARK position. When the automatic transmission is in the PARK position and the brake pedal is not depressed, the IPC illuminates the APPLY BRAKE TO SHIFT indicator in the Drivers Information Center (DIC). When the driver presses the brake pedal, the contacts in the stoplamp switch open, de-energizing the automatic transmission shift interlock solenoid. This allows the shift lever to be moved out of the PARK position. Once the brake pedal is depressed, the PCM sends a class 2 message to the IPC and the APPLY BRAKE TO SHIFT indicator is turned off.