When diagnosing the Engine Coolant Temperature (ECT) sensor, thorough testing is crucial before attributing driveability issues to the sensor. Similar to the IAT sensor, the ECT sensor, a thermistor, experiences resistance changes with temperature fluctuations. Positioned in the engine cooling system near the thermostat housing, it monitors coolant temperature, enabling the PCM to calculate the engine operating temperature. Circuit faults in the ECT sensor can trigger trouble codes, and issues may lie in wiring, connections, or the sensor itself. Some engines feature two nearly identical coolant temperature sensor units-one for the instrument panel temperature gauge and the other for the Electronic Engine Control (EEC) system. Disconnecting the ECT sensor and using an ohmmeter reveals resistance values, approximately 40,500 ohms at 65 degrees F and lower resistance at operating temperature. Confirming correct resistance, check for reference voltage, aiming for an open-circuit voltage around 5 volts from the PCM to the sensor connector. When replacing the sensor, wait for engine cooldown, wrap threads with Teflon sealing tape to prevent leakage, disconnect the electrical connector, unscrew the old ECT sensor, install the new sensor promptly, secure it tightly, reconnect the electrical connector, and check coolant levels, adding if necessary. Finally, start the engine, allow it to reach normal operating temperature, and inspect for coolant leaks, checking the expansion tank's coolant level after the engine has warmed up and cooled down.
Posted by FordPartsGiant Specialist