Circuit/System Description

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

When the ignition switch is placed in the START position, a discrete signal is supplied to the K9 Body Control Module (BCM) notifying it that the ignition is in the START position. The BCM then sends a message to the K20 Engine Control Module (ECM) that crank has been requested. The K20 Engine Control Module then verifies that the transmission is in Park/Neutral. If it is, the K20 Engine Control Module then supplies 12 V to the control circuit 4325 of the KR27C Engine Restart Relay. When this occurs, B+ battery voltage is supplied through the switch of the KR27C Engine Restart Relay circuit 4358 to engage starter pinion. If the voltage is out of range or there is an open/high resistance condition on control circuit 4325 or ground circuit 6450 the fault will set the appropriate DTC during engine cranking.