Circuit/System Description
WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
The adaptive cruise module (ACM) monitors the ignition 1 voltage circuit to determine if the voltage is within the normal operating range. When the ACM detects that the ignition 1 voltage is below 9.2 V or above 16 V, the DTC C0800 sets.