Skylark L4-138 2.3L DOHC VIN D MFI QUAD 4 (1989)
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Engine Coolant Temperature Sensor
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 ECM sends a 5.0 volt signal to the coolant temperature sensor through a resistor in the computer 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.
