The Brake Transmission Shift Interlock (BTSI) is designed to prevent shifting out of PARK without pressing the brake pedal. The BTSI solenoid is energized when the ignition switch is in RUN, BULB TEST, or START and is de-energized when the brake pedal is pressed. The stop lamp switch receives ignition voltage in RUN, BULB TEST, or START from the BTSI Fuse. The Stoplamp Switch is normally closed, providing voltage to circuit 1135 through the BTSI Solenoid, energizing the solenoid and mechanically locking the Transmission Shift Lever whenever it is in PARK. When the brake pedal is pressed, the Stoplamp Switch is open, removing voltage from circuit 1135 to the BTSI Solenoid. This de-energizes the BTSI Solenoid, allowing the vehicle to be moved out of the PARK position.

The Brake Transmission Shift Interlock (BTSI) is designed to prevent shifting out of PARK without pressing the brake pedal. The BTSI solenoid and the Park Lock Solenoid are energized when the ignition switch is in RUN, BULB TEST, OFF, or START. When the Park Lock Solenoid is energized, the mechanical lock connected to this solenoid is pulled away from the shifter. The Stoplamp Switch receives ignition voltage in RUN, BULB TEST, OFF, or START from the BTSI Fuse and is normally closed, providing voltage to circuit 1135 through the BTSI Solenoid, energizing the solenoid and mechanically locking the Transmission Shift Lever whenever it is in PARK. When the brake pedal is pressed, the Stoplamp Switch is open, removing voltage from circuit 1135 to the BTSI Solenoid. This de-energizes the BTSI Solenoid and the mechanical lock connected to the BTSI Solenoid pulls back from the shifter, allowing shifting.