Shift Interlock Systems: Description/Operation

With transmission shift lever in Park position and brake pedal at rest voltage is supplied from BRAKE fuse through Pink/White wire to the antilock brake switch, from the switch through the Purple wire to the brake/shift interlock relay contact, also from the TURN-B/U fuse through the Dark Blue wire to the park/neutral position switch, from the switch through the Light Blue/Black wire to the brake/shift interlock relay coil, voltage to the Dark Green/White wire. The BTSI solenoid can be overridden manually by setting the parking brake, placing the ignition switch in the OFF position and moving the selector lever to NEUTRAL. The vehicle can then be started. Relay coil ground is through the Black wire at the instrument panel ground.

When the brake pedal is depressed the antilock brake switch contacts open interrupting the voltage supply to the brake/shift interlock relay, the BTSI solenoid coil collapses allowing the transmission selector lever to be moved from the PARK position and the brake pedal is not at rest, voltage supply to the relay coil is interrupted and the BTSI solenoid coil collapses allowing the selector lever to be moved normally between reverse and forward gear ranges.