The Steering Column Brake Transmission Shift Interlock (BTSI) Solenoid 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 FUSE 39 through circuit 39. The stop lamp switch is normally closed, providing voltage to circuit 1135 and then through circuit 420 to the park switch. The park switch is closed only when the transmission is in PARK, allowing voltage to then travel thorough it to circuit 1627 and then to the BTSI solenoid. Voltage energizes the solenoid and mechanically locks, the transmission shift lever. When the brake pedal is pressed, the stop lamp switch opens, removing voltage from the BTSI solenoid. The BTSI solenoid is de-energized, which allows the shifter to be moved out of PARK. Ground for the BTSI is supplied by circuit 150.

The Automatic Transmission Shift Interlock Control (BTSI) Solenoid 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 FUSE 39 through circuit 39. The stop lamp switch is normally closed in PARK, providing voltage through circuit 1135 to the BTSI solenoid. Voltage energizes the solenoid and mechanically locks the transmission shift lever. When the brake pedal is pressed, the stop lamp switch open, removing voltage from the BTSI solenoid. The BTSI solenoid is de-energized, which allows the shifter to be moved out of PARK position. Ground for the BTSI is supplied by circuit 150.