Engine Coolant Temperature Sensor - Radiator Outlet
The Engine Coolant Temperature (ECT) sensor is located in the radiator outlet. The sensor is a sealed in the radiator outlet with an O-ring seal. The ECT sensor is a push fit in the radiator outlet and rotated clockwise to lock in position.
The radiator outlet ECT sensor provides the Powertrain Control Module (PCM) and the Instrument Cluster (IC) 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 IC uses the temperature information for temperature gauge operation. The engine coolant temperature signal is transmitted on the FlexRay by the PCM for use by the IC and other systems.
The ECT sensor circuit consists of a voltage divider which incorporates a Negative Temperature Coefficient (NTC) resistor within the ECT sensor. The input to the ECT sensor is a reference voltage supplied through a resistor within the PCM. The ground from the ECT sensor is also connected to the PCM which measures the voltage across the ECT sensor. As the engine coolant temperature rises the resistance of the ECT sensor decreases and vice versa. The output voltage from the ECT sensor changes as the NTC resistor allows more current to pass to ground relative to the temperature of the engine coolant. The PCM calculates the engine coolant temperature from a map of ECT sensor voltage against temperature.
The PCM adjusts fuel delivery for the measured engine coolant temperature to make sure that the optimum efficiency 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 fuel 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°C (140°F) engine coolant temperature for fuelling purposes.