GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Firebird 🢒 Steering 🢒 Steering Wheel and Column - Tilt 🢒 Automatic Transmission Shift Lock Control Circuit Description
    • The brake/transmission shift interlock requires that the brake pedal be depressed and the ignition switch be placed in the RUN or START position before the transmission may be shifted from the park position. When the vehicle is in the RUN or START position, voltage is supplied to the Brake Transmission Shift Interlock (BTSI) solenoid through the GUAGES Fuse 9, circuit 39, the stoplamp switch, and circuit 1135. Ground is provided to the BTSI solenoid through G110, circuit 451, the park neutral position switch PARK position, and circuit 434/816. When the BTSI solenoid is energized there is a restrictor arm that holds the shift lever arm in place. When the brake pedal is depressed, the switch within the stoplamp switch opens cutting off voltage to the BTSI solenoid. When the BTSI solenoid is de-energized the restrictor arm moves clear of the shift lever arm. This allows movement of the park neutral position switch from the PARK position to any other position.
    • If the vehicle is in the NEUTRAL position the gear selector will not shift until the brake pedal is depressed. This is similar to the PARK position as described above.
    • In order to override the shift interlock system turn the ignition switch to the OFF position. This removes battery voltage from the BTSI solenoid, de-energizing the solenoid allowing the vehicle to shift.