Circuit Description
WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) monitors the key in ignition switch signal circuit. When the key is in the ignition, the ignition switch closes and the key in ignition switch signal circuit is pulled low. When the key is not in the ignition, the ignition switch opens and the signal circuit is high.