The IAT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as inlet air temperatures increase, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases.
The IAT sensor provides an input voltage to the Electronic Control Module (ECM) indicating the density of the air entering the intake manifold based upon intake manifold temperature. At key-on, a 5volt power circuit is supplied to the sensor from the ECM. The sensor is grounded at the ECM through a low-noise, sensor-return circuit.
Removal & Installation
- Disconnect the electrical connector form the Intake Air Temperature (IAT) sensor.
- Clean any dirt from the air inlet tube at the sensor base.
Gently lift the small plastic release tab and rotate the sensor about
turn counter-clockwise to remove.
- Check the condition of the sensor O-ring.
- Clean the sensor mounting hole.
- Position the sensor into the intake air tube and rotate clockwise until the release tab clicks into place.
- Install the electrical connector.
- Turn the ignition off. If possible, allow the vehicle to sit with the ignition off for more than 8 hours in an environment where the temperature is consistent and above 20°F (-7°C).
- Test drive the vehicle. The vehicle must exceed 30 mph (48 km/h) during the test drive. Do not cycle the ignition off when the test drive is completed.
- With a scan tool, select View DTCs.
- If a DTC is not active, perform the following:
- Refer to any Technical Service Bulletins (TSBs) that may apply.
- Review the scan tool Freeze Frame information. If possible, try to duplicate the conditions under which the DTC set.
- With the engine running at normal operating temperature, monitor the scan tool parameters related to the DTC while wiggling the wire harness. Look for parameter values to change and/or a DTC to set. Turn the ignition off.
Visually inspect the related wire harness. Disconnect all the related harness connectors. Look for any chafed, pierced, pinched, partially broken wires and broken, bent, pushed out, or corroded terminals. Perform a voltage drop test on the related circuits between the suspected inoperative component and the ECM.
CAUTIONDo not probe the ECM harness connectors. Probing the ECM harness connectors will damage the ECM terminals resulting in poor terminal to pin connection. Install Miller Special Tool No. 8815 to perform diagnosis.
- Inspect and clean all ECM, engine, and chassis grounds that are related to the most current DTC.
- If numerous trouble codes were set, use a wire schematic and look for any common ground or supply circuits.
- For any Relay DTCs, actuate the Relay with the scan tool and wiggle the related wire harness to try to interrupt the actuation.
- For intermittent Evaporative Emission trouble codes perform a visual and physical inspection of the related parts including hoses and the Fuel Filler cap.
- Use the scan tool to perform a System Test if one applies to failing component. A co-pilot, data recorder, and/or lab scope should be used to help diagnose intermittent conditions.