Express 1/2 Ton Van V8-305 5.0L VIN M SFI (1998)
Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection
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The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant stream.
Low coolant temperature produces a high resistance (100,000 ohms at -40°C (-40°F) while high temperature causes low resistance (70 ohms at
130°C (266°F).
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The VCM supplies a 5V signal to the engine coolant temperature sensor through a resistor in the VCM and measures the voltage. The voltage will
be high when the engine is cold, and low when the engine is hot. By measuring the voltage, the VCM calculates the engine coolant temperature.
Engine coolant temperature affects most systems the VCM controls.
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The scan tool displays engine coolant temperature in degrees. After engine start-up, the temperature should rise steadily to about 90°C (194°F)
then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air
temperature displays should be close to each other. A fault in the engine coolant sensor circuit should set DTC P0117 or DTC P0118.
