Shift Interlock System (Column Shift)

The automatic transmission shift lock control system is a safety device that prevents an inadvertent shift out of Park when the engine is running. The driver must press the brake pedal before moving the gearshift lever out of the Park position. The system consists of the following components:

• The Brake Transmission Shift Interlock (BTSI) solenoid (also known as "shift lock solenoid").
• The automatic transmission shift lock control switch (part of stoplamp switch).
• The Transmission Range (TR) switch, also called Park/Neutral Position (PNP) switch.

With the ignition switch in the ON position, battery voltage is supplied to the stoplamp switch. The circuit continues through the normally closed switch to the BTSI solenoid. The PNP switch provides a path to ground for the BTSI solenoid when in the Park position. With the BTSI solenoid energized, the gearshift lever is mechanically locked in the Park position. When the driver presses the brake pedal, the contacts in the stoplamp switch open, de-energizing the BTSI solenoid. This allows the gearshift lever to move from the Park position.