Engine Coolant Temperature (ECT) Sensor - Radiator Outlet
The ECT sensor is located in the radiator outlet, The sensor is a sealed in the radiator outlet with an O-ring seal. The sensor is a push fit in the radiator outlet and rotated clockwise to lock in position.
The radiator ECT sensor provides the PCM and the instrument cluster with engine coolant temperature status.
The PCM uses the temperature information for the following functions:
- Fueling calculations
- Limit engine operation if engine coolant temperature becomes too high
- Cooling fan operation.
The instrument cluster uses the temperature information for temperature gauge operation. The engine coolant temperature signal is transmitted on the high speed CAN powertrain systems bus by the PCM for use by the instrument cluster and other systems.
The ECT sensor circuit consists of a voltage divider which incorporates a negative Temperature Coefficient (NTC) thermistor within the ECT sensor. The input to the sensor is a 5V reference voltage supplied through a resistor within the PCM. The ground from the sensor is also connected to the PCM which measures the voltage across the sensor. As the engine coolant temperature rises the resistance of the sensor decreases and vice versa. The output voltage from the sensor changes as the thermistor allows more current to pass to ground relative to the temperature of the coolant. The PCM calculates the coolant temperature from a map of sensor voltage against temperature.
The PCM adjusts fuel delivery for the measured engine coolant temperature to ensure optimum driveability at all times. The engine will require more fuel when it is cold to overcome fuel condensing on the cold metal surfaces inside the combustion chamber. To achieve a richer air/fuel ratio, the PCM extends the injector opening time. As the engine warms up the air/fuel ratio is leaned off.
If the ECT sensor fails, the following symptoms may be observed:
- Difficult cold starting
- Difficult hot starting
- Reduced engine performance
- Temperature gauge inoperative or inaccurate reading.
In the event of an ECT sensor signal failure, the PCM applies a default value of 60°Celsius (140°F) engine coolant temperature for fuelling purposes.