Shift Interlock: Description and Operation
SHIFT INTERLOCKWhen the Ignition Switch is in the "ON" position or during Retained Accessory Power, the shift interlock system prevents the driver from shifting the vehicle from park unless the brake pedal is depressed. Once the brake pedal is depressed, the solenoid is de-energized. The restrictor arm moves clear of the shift lever arm, allowing the gear selector to operate normally.
The shift interlock system can be overridden and the vehicle can be shifted by turning the Ignition Switch to "OFF." This removes battery voltage at the solenoid, leaving it de-energized.
BRAKE TO SHIFT TELLTALE (BUICK ONLY)
On Buick only, the Park/Neutral Position Switch also contains a Transaxle Range Switch. This is a multi-signal switch which sends information relative to gear selector position to the PCM via 4 discrete circuits. The PCM in turn, sends a signal over the UART data line to the Instrument Cluster. If the Instrument Cluster sees a "Park" signal from the PCM, it turns on the BRAKE TO SHIFT telltale. If it receives any other signal, the telltale will not light.
Important
^ Open any door on vehicles equipped with Retained Accessory Power (RAP) to remove battery voltage at the solenoid.