Circuit Operation

When the ignition switch is ON or when retained accessory power is active, the shift interlock system prevents the driver from shifting the vehicle from park until the brake pedal is depressed. Pressing the brake pedal de-energizes the Brake Transaxle Shift Interlock (BTSI) solenoid. The restrictor arm moves clear of the shift lever arm allowing the gear selector to operate normally.

To overwide the shift interlock system and shift the vehicle turn the ignition switch to OFF. This removes battery voltage at the BTSI solenoid, leaving the solenoid de-energized.

"BRAKE TO SHIFT" Indicator (Buick Only)
On Buick only the Park Neutral Position (PNP) switch also contain a transaxle range switch. This component is a multi-signal switch which sends information relative to gear selector position to the PCNI via four discrete circuits.

The Powertrain Control Module (PCM) in turn, sends a signal over the UART data line to the instrument cluster. If the instrument cluster receives a Park signal from the PCM, it turns on the "BRAKE TO SHIFT" indicator. If it receives any other signal, the indicator does not light.

Important:
On vehicles equipped with Retained Accessory Power (RAP) open any door to remove battery voltage at the solenoid.