Circuit/System Description
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The low engine coolant level indicator lamp on the instrument panel cluster (IPC) is controlled by the body control module (BCM) through the low speed GM LAN Serial Data line to the engine control module (ECM). When the engine coolant level switch is open for 30 seconds or longer indicating low coolant, the BCM will signal the ECM to turn ON the Coolant level lamp. The lamp will also illuminate for approximately 3 seconds during the display test at the start of each ignition cycle.