Circuit Operation

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 START" or "START" and is de-energized when the brake pedal is depressed.

The BTSI/STOP LP Brake Switch receives Ignition Voltage from the Turn B/U Fuse in "RUN," "BULB TEST" or "START" The BTSI Switch is part of the BTSI/STOP LP Brake Switch and is normally closed, providing voltage through CKT 1135 to the BTSI Solenoid, energizing the Solenoid and mechanically locking the Transmission Shift Lever whenever it is in "PARK."

When the brake pedal is depressed, the BTSI Switch opens, removing voltage from CKT 1135 to the BTSI Solenoid. This de-energizes the BTSI Solenoid, allowing the Shift Lever to be moved out of the "PARK" position.