Engine Coolant Temperature (ECT) sensor — replacement and testing
Replacement
Warning: Wait until the engine has cooled completely before beginning this procedure.
Caution: Handle the coolant sensor with care. Damage to this sensor will affect the operation of the entire fuel injection system.
1. Make sure the ignition key is in the Off position.
2. Drain approximately 1/4 of the engine coolant (see Tune-up and routine maintenance), to bring it below the level of the ECT sensor.
3. Disconnect the electrical connector a carefully unscrew the sensor from the rear (driver’s end) of the cylinder head (see illustration). Also be sure to withdraw and discard
i. 3 Location of the ECT sensor
Note: On these models, it is NOT necessary to wrap the threads of the new sensor with Teflon sealing tape to prevent leakage — the new 0-ring should be able to accomplish this sufficiently
4. Ensure a new sealing ring is used upon installation.
5. Installation is the reverse of removal. Tighten the sensor securely.
Testing
Note: A food thermometer or laser gauge can be used to check the water temperature
6. Remove the ECT sensor (see previous Steps).
7. Partially submerge the sensor in a suitable pan/pot of water (only the end of the sensor submerged — up to the hex fitting), making sure the electrical terminals are dry. The sensor’s voltage will be measured with the water’s varying temperature. This step is performed easiest with sensor suspended by a length of wire.
8. Using a digital volt or ohm meter set to measure resistance, measure between the two terminals of the ECT sensor. With the water in the pot/pan at room temperature (68 degrees-F), resistance should be 2.32k to 2.59k ohms. With the water heated to 176 degrees-F, resistance should be 0.310k to 0.326k ohms.
9. If the resistance of the sensor in water does not fall within the specified range at room temperature or when heated, replace the sensor.