Brake/Transmission Shift Interlock (BTSI) System

This system does not allow shift lever to be moved out of Park unless brake pedal is pressed. With brake pedal released and ignition on, current flows through BTSI solenoid to ground, energizing solenoid. With solenoid energized, a lock pawl protrudes from solenoid, preventing shift lever from being moved.

With brake pedal pressed, current flows through stoplight switch to ground side of solenoid. Under this condition, battery voltage is available on positive and negative sides of solenoid. This causes solenoid to de-energize, releasing lock pawl.