Shift Interlock: Description and Operation

When the Brake Transmission Shift Interlock (BTSI) is energized, the solenoid locks the shift lever mechanism in Park. When not energized, the Steering Column Shift Lever Actuator (W/ Column Shift A/T) or Park Pawl Actuator (W/ Floor Shift A/T) returns to the unlocked position.

The components involved in the BTSI circuit are as follows:
^ Park/Neutral Position And Backup Lamp Switch
- TCC Brake And Cruise Control Release Switch
- Steering Column Shift Lever Actuator (W/ Column Shift A/T) or Park Pawl Actuator (W/ Floor Shift A/T) (BTSI Solenoid)

TURN B/U Fuse 16 supplies battery voltage to the Steering Column Shift Lever Actuator (W/ Column Shift A/T) or Park Pawl Actuator (W/ Floor Shift A/T) via the Park/Neutral Position And Backup Lamp Switch and the TCC Brake And Cruise Control Release Switch. With the Ignition Switch in the Run or Start position, the shift lever in Park, and the brake pedal released, the solenoid is energized. This locks the shift lever in Park.

Note that the BTSI portion of the TCC Brake and Cruise Control Release Switch (pins E & F) is closed with the brakes released. Depressing the brake pedal opens the switch causing the solenoid to de-energize, unlocking the shift lever. The BTSI portion of the PNP switch is closed in Park only. The circuit is not active with the Ignition Switch Off to facilitate towing.