If the following tests indicate that a sensor is good, and not the cause of a driveability problem or OTC, check the wiring harness and connectors between the sensor and the PCM for an open or short circuit. If no problems are found, have the vehicle checked by a dealer service department or other qualified repair shop. The Intake Air Temperature Sensor is a thermistor that changes resistance as temperature changes. The sensor is installed in the intake air duct to sense air temperature. As temperature increases, sensor resistance decreases and vice versa. The PCM uses this information to compute the intake temperature and fine tune fuel metering. A problem in the Intake Air Temperature Sensor circuit fault may be in the circuit wiring or connections or in the sensor itself. With the engine cool, disconnect the Intake Air Temperature Sensor and use an ohmmeter to measure sensor. For example, at 68-degrees F the ohms (Intake Manifold Temperature and Engine Coolant Temperature (ECT) sensors approximate temperature vs. resistance values). Next, start the engine and warm it up until it reaches operating temperature. Turn the engine off, disconnect the sensor and measure the resistance again. It should be lower. If the sensor resistance doesn't change as described, replace it. If the resistance values of the sensor are correct, check for reference voltage from the PCM to the sensor connector. The open-circuit voltage at the sensor connector should be approximately 5 volts. Disconnect the electrical connector, then carefully remove the Intake Air Temperature Sensor from the air intake duct. Be careful not to damage any of the plastic parts. Install and connect the new sensor.
