Hombre XS Space Cab L4-2.2L CPC (1997)
Engine Temperature Sensor: Description and Operation
Engine Coolant Temperature (ECT) Sensor
The Engine Coolant Temperature (ECT) sensor (3) 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).
The PCM supplies a 5 volt signal to the ECT sensor through a resistor in the PCM and monitors the terminal voltage. Since this forms a series
circuit to ground through the ECT sensor, high sensor resistance (low temperature) will result in high PCM terminal voltage. When the resistance
of the ECT sensor is low (high temperature), the terminal voltage will be drawn lower. This terminal voltage indicates engine coolant temperature
to the PCM.
A hard fault in the ECT sensor circuit should set either a DTC P0117 or P0118. Remember, these DTCs indicate a malfunction in the engine
coolant temperature circuit, so proper use of the DTC table may lead to either repairing a wiring problem or replacing the sensor, to properly
repair a problem.
