GM 25037332 Sensor,Engine Coolant Temperature Gage

The Engine Coolant Temperature (ECT) sensor is a thermistor, a resistor which varies the value of its resistance in accordance with temperature changes. The change in the resistance values will directly affect the voltage signal from the sensor to the ECM/PCM. As the sensor temperature increases, the resistance values will decrease and vice versa. Performing the following test will set a diagnostic trouble code and illuminate the Service Engine Soon light. Clear the diagnostic trouble code after performing the tests and making the necessary repairs. The engine coolant temperature sensor threads into a coolant passage at the front of the engine near the thermostat housing. Check the terminals in the connector and the wires leading to the sensor for looseness and breaks. Repair as required. Before checking the engine coolant temperature sensor, check the voltage supply and ground circuits from the ECM/PCM. Disconnect the electrical connector from the engine coolant temperature sensor and connect a voltmeter to the two terminals of the harness connector. Turn the ignition key On-the voltage should read approximately 5.0 volts. If the voltage is incorrect, check the wiring from the engine coolant temperature sensor to the ECM/PCM. If the circuits are good, have the ECM/PCM checked at a dealer service department or other properly equipped repair facility. With the ignition switch OFF, disconnect the electrical connector from the engine coolant temperature sensor. Using an ohmmeter, measure the resistance between the two terminals on the sensor while it is completely cold. Reconnect the electrical connector to the sensor, start the engine and warm it up until it reaches operating temperature, disconnect the connector and check the resistance again. Compare your measurements to the resistance chart. If the sensor resistance test results are incorrect, replace the engine coolant temperature sensor. A more accurate check may be performed by removing the sensor and suspending the tip of the sensor in a container of water. Heat the water on the stove while you monitor the resistance of the sensor. Wait until the engine is completely cool before beginning this procedure. Drain the cooling system. Disconnect the electrical connector from the sensor and carefully unscrew the sensor. Before installing the new sensor, wrap the threads with Teflon sealing tape to prevent leakage and thread corrosion. Installation is the reverse of removal.

Various engine sensors and components have checking procedures,the engine coolant temperature (ECT) sensor is a thermistor that changes resistance with temperature, and a failure in the circuit can cause trouble codes. The resistance should be measured when cold and warm while ensuring reference voltage from PCM is around 5.0 volts for the verification. Manifold Absolute Pressure (MAP) Sensor monitors changes in intake manifold pressure then varies its voltage output accordingly. Look at the reference voltage and signal voltage with the ignition on and engine off, and observe voltage changes as the engine's vacuum changes. Intake Air Temperature (IAT) Sensor acts as a thermistor where you can measure its resistance at different temperatures to make sure it changes as expected. Also, use a scan tool to monitor the IAT sensor for performance. The oxygen sensor in exhaust detects oxygen content which you can check its millivolt signal while warming up your engine. Check whether the oxygen sensor heater has correct voltage or not. Vehicle Speed Sensor (VSS) provides speed data to PCM which can be checked for reference voltage. Depending on the type of engine, Camshaft Sensor and Crankshaft Sensor should be checked for resistance and proper signal output. Finally, Knock Sensors detect engine knock which should be checked for reference voltage and resistance. If any component fails these checks, replacement may be necessary.

First, ensure that the light comes on when the Ignition switch is turned on.

Ensure that the engine is cool and be prepared to catch any coolant loss.

The engine coolant temperature sensor threads into a coolant passage at the front of the engine near the thermostat housing.

If any component fails these checks, replacement may be necessary.

The camshaft sensor and crankshaft sensor, depending on the engine type, should be checked for resistance and proper signal output.

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