Calais L4-151 2.5L VIN U TBI (1989)
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Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Coolant Temperature Sensor (CTS)
The engine coolant temperature sensor is a thermistor that is located in the engine coolant flow. When the coolant temperature is low, the sensor
produces a high resistance. When the coolant temperature is high, the sensor produces a low resistance.
The computer sends a 5.0 volt signal to the coolant temperature sensor through a resistor in the ECM and measures the voltage. The voltage will be high
or low depending on coolant temperature. By varying the voltage, the computer will sense engine coolant temperature.