The brake transaxle shift interlock (BTSI) system prevents the transaxle from being shifted out of the PARK position without the brake pedal being depressed while the ignition is in the RUN mode. When the brake pedal is depressed, the BCM receives the brake switch information over the serial data link from the engine controller, and energizes the shift lock control solenoid which allows the transaxle control assembly to be shifted out of PARK. The shift lock control solenoid is located on the transaxle control assembly. The transaxle can be shifted out of PARK without the brake pedal being depressed, if the ignition key is in ACC.

The parklock switch operates the vehicle stop lamps and also signals the body control module (BCM) over the serial data link. The switch is normally open when the brake pedal is in the released position. When the brake pedal is depressed, the pressure on the switch plunger is released and the switch closes. When the brake pedal is depressed, and the transaxle control assembly is in the PARK position, and the BCM energizes the shift lock control solenoid allowing the transaxle to be shifted out of PARK.