Circuit Description
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
When ignition is turned on, Sensing and Diagnostic Module (SDM) performs tests to diagnose critical internal malfunctions. SDM provides input power to SIS. When input power is first detected, SIS responds by performing internal diagnostics. Next, SIS sends an identification message to SDM.
SDM will consider this to be a valid identification if response time is less than 5 seconds after SIS powers up. SIS continually communicates a status message to SDM. SDM can reset SIS by removing and applying power to it.