Engine Coolant Level Sensor

When the coolant level in the coolant expansion tank is sufficient, the magnetic float is in the top position. In this position the magnetic field closes the switch contacts in the coolant level sensor. When the coolant level drops significantly below the MIN cold fill coolant level, the magnetic float descends, thus the switch contacts disconnected. The open circuit is sensed by the BCM  /GWM  , which sends a signal to the Instrument Cluster (IC) to display the "Coolant Level Low" warning message. The message is sent on the HS CAN  comfort systems bus.