GM Service Manual Online
For 1990-2009 cars only

Moving the ignition switch to the Start position sends a 12 V signal through the PNP switch or the Clutch Pedal Position switch and on through the Theft Deterrent relay to the BCM for ground. The BCM verifies that it has received a (valid theft password). When the Theft Deterrent relay is energized it completes the B+ voltage circuit to the starter solenoid S terminal.