GM Service Manual Online
For 1990-2009 cars only

The Brake Transmission Shift Interlock (BTSI) is a park lock system. The BTSI system prevents the vehicle's transaxle from shifting out of PARK unless you depress the brake pedal fully. When you depress the brake pedal, the BTSI electromagnet releases the lock pawl. The released lock pawl enables the following events to occur:

    • The shift lever moves.
    • The shift cable operates.

When the vehicle requires service, you may override the BTSI system by turning the ignition lock OFF. Turning the ignition lock OFF causes the following events to occur:

    • The battery voltage removes from the electromagnet.
    • The electromagnet is left deenergized.