Shift Interlock: Description and Operation

DESCRIPTION








The Brake/Transmission Shift Interlock system consists of an electro-magnetic solenoid mounted to the steering column (Fig. 304). The solenoid's plunger consists of an integrated hook, which operates the shift lever pawl (part of shift lever assembly), and a plunger return spring (Fig. 305). The solenoid also has an integrated bracket, which facilitates fastening to the steering column.

OPERATION





The Brake/Transmission Shift Interlock (BTSI) Solenoid prevents the transmission shift lever from being moved out of PARK (P) unless the brake pedal is applied. The BTSI solenoid is hard wired to and controlled by the Intelligent Power Module (IPM). Battery voltage is applied to one side of the solenoid with the ignition key is in either the ON/RUN or START positions (Fig. 306). The ground side of the solenoid is controlled by a driver within the IPM. It relies on voltage supplied from the stop lamp switch to the stop lamp sense circuit within the IPM to tell when the brake pedal is depressed. When the brake pedal is depressed, the ground circuit opens, de-energizing the solenoid. When the brake pedal is released, the ground circuit is closed, energizing the solenoid.








When the ignition key is in either the ON/RUN or START positions, the BTSI solenoid is energized, and the solenoid plunger hook pulls the shift lever pawl into position, prohibiting the shift lever from moving out of PARK (P) (Fig. 307). When the brake pedal is depressed, the ground circuit opens, de-energizing the solenoid. This moves the gearshift lever pawl out of the way (Fig. 308), allowing the shift lever to be moved into any gear position.
A conventional mechanical interlock system is also used. This system manually prohibits shifter movement when the ignition switch is in the LOCK or ACC positions. Solenoid operation is not required in these key positions. When the ignition key is in the OFF position, the gearshift lever is unrestricted, and able to move into any gear position (during towing, dead battery, etc.).





For intended BTSI system operation, refer to the chart: