[my99cavy]

Fig. 1: The ECT sensor is located in the water outlet housing, adjacent to where the upper radiator hose connects to the engine

Fig. 2: ECT sensor location-2.4L engine


Fig. 3: ECT sensor location-1998-00 2.2L engine

The Engine Coolant Temperature (ECT) sensor resistance changes in response to engine coolant temperature. The sensor resistance decreases as the coolant temperature increases, and increases as the coolant temperature decreases. This provides a reference signal to the PCM, which indicates engine coolant temperature. The signal sent to the PCM by the ECT sensor helps the PCM to determine spark advance, EGR flow rate, air/fuel ratio, and engine temperature. The ECT also is used for temperature gauge operation by sending it's signal to the instrument cluster.
The ECT is a two wire sensor, a 5-volt reference signal is sent to the sensor and the signal return is based upon the change in the measured resistance due to temperature.

TESTING
See Figures 4, 5 and 6

Fig. 4: Detach the connector on the ECT sensor


Fig. 5: Measure the resistance across the ECT terminals on the sensor


Fig. 6: ECT sensor resistance value chart

1. Disconnect the engine wiring harness from the ECT sensor.
2. Connect an ohmmeter between the ECT sensor terminals.
3. With the engine cold and the ignition switch in the OFF position, measure and note the ECT sensor resistance.
4. Connect the engine wiring harness to the sensor.
5. Start the engine and allow the engine to reach normal operating temperature.
6. Once the engine has reached normal operating temperature, turn the engine OFF.
7. Once again, disconnect the engine wiring harness from the ECT sensor.
8. Measure and note the ECT sensor resistance with the engine hot.
9. Compare the cold and hot ECT sensor resistance measurements with the accompanying chart.
10. If readings do not approximate those in the chart, the sensor may be faulty