Coolant Level Sensor: Description and Operation

COOLANT LEVEL TELLTALE - The low engine coolant level switch is located in the bottom of the coolant recovery reservoir. The low engine coolant level switch is used to detect engine coolant in the coolant recovery reservoir dropping below a certain level. The switch is a normally open switch that closes when the engine coolant in the reservoir is above a certain level. The switch is supplied ignition voltage, which is used as a switch input to the PCM. When the coolant in the coolant recovery reservoir is full, the low engine coolant level switch closes (ignition voltage at PCM). The PCM turns On the Coolant Level telltale (with low coolant level) by sending a message to the I/P cluster over the Class II link.