Diagnostic Aids

WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

Use a scan tool to verify there are no brake pedal position sensor and/or transmission internal mode switch (IMS) DTCs set that could cause the BCM not to provide battery voltage to the A/T shift lock control solenoid.
If the automatic transmission shift lock control circuit is shorted to battery positive voltage, the automatic transmission shift lock control solenoid will be inoperative. The vehicle will shift out of PARK without depressing the brake pedal.
Perform the tests while wiggling the wires and connectors. This may often cause an intermittent malfunction to appear. Refer to Testing for Intermittent Conditions and Poor Connections .