Circuit Description
WARNING: This page is about a different car, the 2003 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
Moving the ignition switch to the CRANK position sends a 12 V signal to the PCM Ignition Crank Sense. The PCM verifies that the transmission is in the PARK or NEUTRAL position. The PCM then grounds the control circuit of the START 1 relay. When the START 1 relay is energized it allows voltage to the starter solenoid S terminal.