GM 25037334 Sensor Assembly, Intake Air Temperature

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The Intake Manifold Temperature (IMT) sensor is a thermistor, a resistor that changes its resistance value with temperature. The voltage signal from the sensor to the PCM will be directly affected by this change in the resistance values. Resistance values decrease as the sensor temperature increases. The resistance values, however, increase as the sensor temperature goes down. It should be noted that only 1996 through 2000 models are equipped with an IMT sensor. This test sets a diagnostic trouble code and illuminates the Service Engine Soon light. Clearing the diagnostic trouble code after performing tests is mandatory together with making necessary repairs. One can find the Intake Manifold Temperature (IMT) sensor installed either in the air intake duct near the air cleaner or in it. Check that there are no loose terminals in the connector and breakages on wires leading to the sensor first of all. Make repairs where necessary. Before checking intake manifold temperature sensor, check PCM voltage supply and ground circuits. Disconnect electrical connector from IMT Sensor and connect positive lead of voltmeter to tan wire terminal and negative lead to black wire terminal at harness connector. Turn ignition switch ON- voltage reading should be approximately 5.0 volts. If voltage is not correct; check wiring between sensor and PCM. If circuits are good, then have PCM checked at dealer service department or other properly equipped repair facility. Disconnect electrical connector from IMT sensor with ignition switch OFF. With an ohmmeter measure resistance between two Intake Manifold Temperature sensor terminals on sensor while completely cold (50 to 80-degrees F). Reconnect electrical connector to sensor start engine and warm up until operating temperature is reached (180 to 200-degrees F), disconnect connector again, measure resistance. Compare your measurements against resistance chart for this vehicle. Should there be incorrect results of this test, replace intake manifold temperature sensor. A more accurate check may be performed by removing air intake duct and heating the sensor, with a heat gun or hair dryer while you monitor the resistance of the sensor. Disconnect electrical connector from sensor. Carefully remove sensor from air intake duct or air cleaner assembly. Installation is reverse of removal.

To test the resistance of the IAT sensor, disconnect the electrical connector from the sensor. Using an ohmmeter, measure the resistance between the two IAT sensor terminals while it is completely cold (around 50 to 50 degrees F). Then, reconnect the electrical connector, start the engine, and warm it up to operating temperature (around 180 to 200 degrees F). Disconnect the connector again and check the resistance. Compare these measurements to a resistance chart.