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 the following positions:

The BTSI solenoid is de-energized when the brake pedal is depressed. The BTSI Fuse sends ignition voltage to the stop lamp switch in the following positions:

The stop lamp switch is normally closed, providing voltage through CKT 1135 to the BTSI solenoid. The voltage energizes the BTSI solenoid and mechanically locks the transmission shift lock whenever the transmission shift lever is in PARK. When the brake pedal is depressed, the stop lamp switch opens, removing voltage from the CKT 1135 to the BTSI solenoid. This de-energizes the BTSI solenoid, allowing the vehicle to moved out of the PARK position.