Cadillac 25037334 Sensor Assembly, Intake Air Temperature

The Intake Manifold Temperature (IMT) 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 PCM. As the sensor temperature increases, the resistance values will decrease. As the sensor temperature decreases, the resistance values will increase. Only 1996 through 2000 models are equipped with an IMT sensor. 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 Intake Manifold Temperature sensor is mounted either in the air intake duct near the air cleaner or in the air cleaner. Check the terminals in the connector and the wires leading to the sensor for looseness and breaks. Repair as required. Before checking the intake manifold temperature sensor, check the voltage supply and ground circuits from the PCM. Disconnect the electrical connector from the IMT sensor and connect the positive lead of a voltmeter to the tan wire terminal and the negative lead to the black wire terminal at 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 sensor to the PCM. If the circuits are good, have the PCM checked at a dealer service department or other properly equipped repair facility. With the ignition switch OFF, disconnect the electrical connector from the IMT sensor. Using an ohmmeter, measure the resistance between the two Intake Manifold Temperature sensor terminals on the sensor while it is completely cold (50 to 80-degrees F). Reconnect the electrical connector to the sensor, start the engine and warm it up until it reaches operating temperature (180 to 200-degrees F), 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 intake manifold temperature sensor. A more accurate check may be performed by removing the air intake duct and heating the sensor, with a heat gun or hair dryer while you monitor the resistance of the sensor. Disconnect the electrical connector from the sensor. Carefully remove the sensor from the air intake duct or the air cleaner assembly. Installation is the 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.