Intake Air Temperature Sensor (IAT)

The Intake Air Temperature Sensor (IAT) is used by the ECU to determine the temperature of the air entering the engine. This is used in conjunction with the MAP sensor to determine the density and volume of air entering the engine to make the proper fuel adjustments to maintain the correct air/fuel ratio. The Intake Air Temperature Sensor is a temperature dependant resistor (thermistor). The resistance of the thermistor decreases as the intake air temperature increases:


1. Jump the service check connector and verify that the Check Engine Light shows code 10.
2. Turn the ignition switch off and disconnect the 2 pin connector from the Intake Air Temperature Sensor (IAT).
3. Measure the resistance between the 2 terminals on the IAT sensor.
4. Is there between 0.4 - 4.0 ohms resistance? If not, the Intake Air Temp. Sensor is faulty and needs replacement. If yes, continue..
5. Turn the ignition switch on (do not start engine).
6. Measure the voltage between the lower terminal (red/yellow on connector in image) and body ground. Is there approximately 5 volts?
- If yes, measure the voltage between the lower terminal (shown as red/yel in image) and upper terminal (shown as grn/wht in image). If there is NOT approximately 5 volts, repair the short in the upper terminal wire (shown as grn/wht in image).
- If not, check for continuity from lower terminal (shown as red/yel) to correct pin on ECU. If continuity does NOT exist, repair short in wire. If continuity DOES exist, the ECU may be faulty or ROM settings may be out of acceptable range.

NOTE: Wire colors on 2 pin connector shown are for OBD1 harnesses. You may need to consult the proper wire diagram for your vehicle for accurate wire color.

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