See Figure 1
The ECT sensor is located either in the heater supply tube at the rear of the engine, or in the lower intake manifold. The ECT sensor is a thermistor (changes resistance as temperature changes). The sensor detects the temperature of engine coolant and provides a corresponding signal to the PCM. From this signal, the PCM will modify the air/fuel ratio (mixture), idle speed, spark advance, EGR and canister purge control. When the engine coolant is cold, the ECT sensor signal causes the PCM to provide enrichment to the air/fuel ratio for good cold drive-away; as engine coolant warms up, the voltage will drop.
See Figures 2, 3, 4 and 5
- Disconnect the temperature sensor.
- Connect an ohmmeter between the sensor terminals and set the ohmmeter scale on 200,000 ohms.
- Measure the resistance with the engine off and cool and with the engine running and warmed up. Compare the resistance values obtained with the chart.
- Replace the sensor if the readings are incorrect.
- Remove the sensor from the vehicle.
- Immerse the tip of the sensor in container of water.
- Connect a digital ohmmeter to the two terminals of the sensor.
- Using a calibrated thermometer, compare the resistance of the sensor to the temperature of the water. Refer to the engine coolant sensor temperature vs. resistance illustration.
- Repeat the test at two other temperature points, heating or cooling the water as necessary.
- If the sensor does not meet specification, it must be replaced.
REMOVAL & INSTALLATION
See Figures 6, 7 and 8
- Drain the engine cooling system slightly.
- Disconnect the negative battery cable.
- Detach the wiring connection from the sensor.
- Remove the coolant temperature sensor.
- Clean the sensor area of any debris.
- Install a new sensor. Tighten the 6-14 ft. lbs. (8-19 Nm).
- Attach the sensor wiring to the unit.
- Connect the negative battery cable.
- Fill the engine cooling system with a 50/50 coolant water mixture.
- Start the engine and top off the cooling system.