Engine Coolant Temperature Sensor
The Engine Coolant Temperature (ECT) sensor is Negative Temperature Coefficient (NTC) thermistor that allows the Powertrain Control Module (PCM) to monitor the engine coolant temperature.
The ECT sensor circuit consists of a voltage divider which incorporates a Negative Temperature Coefficient (NTC) resistor. The input to the ECT sensor is a 5V 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 PCM calculates the engine coolant temperature from a map of sensor voltage against temperature.
There are 2 identical ECT sensors installed, which are identified as ECT sensor 1 and ECT sensor 2. Each sensor is secured with a twist-lock and latch mechanism, and is sealed with an O-ring. A 2 pin electrical connector provides the interface between the sensor and the engine wiring harness.
ECT sensor 1
The ECT sensor 1 is installed in the heater manifold, at the rear of the Bank 1 cylinder head. The input from this sensor is used in calibration tables and by other systems.
If there is an ECT sensor 1 fault, the PCM adopts an estimated coolant temperature. On the second consecutive trip with an ECT sensor 1 fault, the PCM illuminates the Malfunction Indicator Lamp (MIL).
ECT sensor 2
ECT sensor 2 is installed in the lower hose connector which attaches to the bottom of the electric thermostat. The input from this sensor is used for On-Board Diagnostics (OBD) and, in conjunction with the input from ECT sensor 1, to confirm that the thermostat is functional.
If there is an ECT sensor 2 fault, the PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive trip.