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:

With the ignition in the ON position, the powertrain control module (PCM) sends the transmission gear position to the body control module (BCM) through a class II message. When the body control module receives the message that the transmission is in the PARK position the body control module energizes the park neutral position switch park signal circuit. Battery voltage is supplied to the automatic transmission shift lock control switch and flows through the normally closed contacts of the switch to the automatic transmission shift lock control solenoid. The automatic transmission shift lock control solenoid is permanently ground and therefore energizes, locking the shift lever in the PARK position. When the driver presses the brake pedal the contacts in the automatic transmission shift lock control switch open. This causes the automatic transmission shift lock control solenoid to de-energize, allowing the driver to move the shift lever out of the PARK position. With the transmission shift lever out of the PARK position the powertrain control module (PCM) sends a class II message to the body control module (BCM) indicating the transmission is out of the PARK position. The body control module then de-energizes the park neutral position switch park signal circuit.