The automatic transmission shift lock control is a safety device that prevents an inadvertent shift out of PARK when the ignition is ON. 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 battery positive voltage is supplied to the automatic transmission shift lock control module. The automatic transmission shift lock control module is also permanently grounded. When the brake pedal is depressed the contacts in the stop lamp switch close and voltage is supplied to the automatic transmission shift lock control module through the shift lock control input signal circuit. With the shift lever in the PARK position the internal park switch contacts are closed allowing voltage to flow to the internal shift lock control solenoid. The internal shift lock control solenoid is permanently grounded within the automatic transmission shift lock control module. With power and ground supplied the shift lock control solenoid energizes. This releases the mechanical lock and allows the shift lever to be moved out of the PARK position. When the shift lever is out of the PARK position the internal park switch contacts open, This de-energizes the automatic transmission shift lock control solenoid. The automatic transmission shift lock control solenoid will not reactivate until the shift lever is returned to the PARK position and the automatic transmission shift lock control module receives an input signal from the stop lamp switch.