Coolant Level Sensor: Description and Operation

Coolant Level Control
The engine cooling system contains an engine coolant level switch to alert the driver in the event of a low coolant level.

When the engine coolant level in the surge tank falls below a certain level, the coolant level switch opens. When the HVAC control module detects an open, or a high voltage level, on the coolant level indicator control circuit for at least 10 seconds, it will send a class 2 message to the radio requesting display of the low coolant level message.

There is approximately a 10 second delay before the HVAC control module sends the class 2 message, to prevent the message from being displayed due to coolant sloshing in the surge tank.