The Brake Transaxle Shift Interlock (BTSI) System is designed to keep the driver from moving the gear selector out of PARK without the brake pedal being depressed. The battery voltage is applied to the BTSI solenoid with the ignition switch in either of the following positions:

With the brake pedal released, the following actions occur:

When the brake pedal is depressed, the battery voltage is no longer applied to the BTSI solenoid. The solenoid de-energizes. This allows the gear selector to move freely from the PARK position.