Forenza L4-2.0L (2004)
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Engine Coolant Temperature Sensor Description
The Engine Coolant Temperature (ECT) sensors 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 degrees C [-40 degrees F]) while high temperature causes low
resistance (70 Ohms at 130 degrees C [266 degrees F]).
The Engine Control Module (ECM) supplies 5 V to the ECT sensor through a resistor in the ECM and measures the change in voltage. The voltage will
be high when the engine is cold, and low when the engine is hot. By measuring the change in voltage, the ECM can determine the coolant temperature.
The engine coolant temperature affects most of the systems that the ECM controls. A failure in the ECT sensor circuit should set a diagnostic trouble
code P0117 or P0118.
Remember, these diagnostic trouble codes indicate a failure in the ECT sensor circuit, so proper use of the chart will lead either to repairing a wiring
problem or to replacing the sensor to repair a problem properly.
