Park Lock Control System (Regal)

WARNING: This page is about a different car, the 2004 Buick Regal, 2004 Buick Century, 2003 Buick Regal, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

The park lock control system is a safety device that prevents an inadvertent shift out of PARK when the ignition is OFF. The system consists of the following components:

The automatic transmission park lock solenoid
The brake to shift relay
The body control module (BCM)
The powertrain control module (PCM)

With the ignition in the OFF position the park lock control solenoid is de-energized. This mechanically locks the shift lever in the PARK position. With the ignition in the ON position, battery voltage is supply to the park lock control solenoid. The control circuit of the park lock solenoid is provided a ground through the brake to shift relay when energized. The body control module (BCM) supplies a ground for the brake to shift relay when the body control module (BCM) receives a class 2 message from the powertrain control module (PCM) indicating the transmission is in the PARK position. This closes the normally open contacts of the brake to shift relay and grounds the park lock control solenoid. This energizes the park lock control solenoid releasing the mechanical park lock.