Description & Operation: Introduction

WARNING: This page is about a different car, the 2002 Pontiac Grand Am, 2002 Oldsmobile Alero, 2001 Pontiac Grand Am, and 2001 Oldsmobile Alero. However, it is still accessible from the selected car via links, so may be relevant.

The automatic transmission shift lock control is a safety device that prevents an inadvertent shift out of Park when the ignition is ON. The driver must press the brake pedal before moving the gearshift lever out of the Park position. The system consists of the following components:

Automatic transmission shift lock control solenoid.
Automatic transmission shift lock control switch (stoplamp switch).
The Park/Neutral Position (PNP) switch.

With the ignition in the ON position, battery positive voltage is supplied to the PNP switch. With the transmission in the Park position, the contacts in the PNP switch are closed. This allows current to flow through the switch to the stoplamp switch. The circuit continues through the normally-closed switch to the A/T shift lock control solenoid. The A/T shift lock control solenoid is permanently grounded. This energizes the A/T shift lock control solenoid, mechanically locking the shift linkage in the PARK position. When the driver presses the brake pedal, the contacts in the stoplamp switch open, de-energizing the A/T shift lock control solenoid. This allows the gearshift lever to move from the Park position.