Standard Models (Non-Alternative Fuels)

CIRCUIT DESCRIPTION
The Intake Air Temperature (IAT) sensor is a thermistor. The control module supplies the IAT sensor a reference voltage on the IAT sensor signal circuit and a ground circuit. When the IAT sensor resistance is high, indicating a cold sensor, the IAT sensor signal voltage remains near the supplied voltage and decreases the signal voltage as the sensor warms. The control module monitors the IAT sensor signal circuit in order to calculate the temperature of the air entering the engine.

This Diagnostic Trouble Code (DTC) is designed to detect an IAT sensor signal voltage higher than the possible range of a normally operating IAT sensor.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0117, P0118, P0125, P0502, P0503, P1114, and P1115 are not set.
^ The vehicle speed is below 3 km/h (2 mph).
^ The Mass Air Flow (MAF) is less than 250 g/s.
^ The coolant temperature is above 85°C (184°F).
^ The engine has been running for more than 100 seconds.

CONDITIONS FOR SETTING THE DTC
The IAT sensor temperature is less than -35°C (31°F) for more than 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
The IAT sensor indicates the temperature of the ambient air which is entering the throttle body. The IAT sensor temperature should read very close to the temperature of the outside air. The IAT sensor temperature should rise gradually as the engine warms up and the underhood temperature increases. If DTC P1111 is set, the problem is intermittent. Check for an open in the IAT sensor circuit. This may be accomplished by moving the PCM harness at various locations and monitoring IAT temperature or IAT voltage on the scan tool. If the voltage varies, look for an open in the area of the harness that caused the variance. Also, a sensor may become skewed or mis-scaled. Refer to Temperature vs Resistance. Temperature VS Resistance

An intermittent may be caused by any of the following conditions:
^ A poor connection
^ Rubbed through wire insulation
^ A broken wire inside the insulation

Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections in Diagrams.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Diagrams.

TEST DESCRIPTION

Steps 1-15:

The numbers below refer to the step numbers on the diagnostic table.
2. If the IAT sensor temperature is less than -39°C (38°F), the conditions for the DTC are still present, and the problem is not intermittent.
3. This test will bypass the IAT sensor and will confirm that the IAT signal circuit and the sensor low reference circuit to the PCM are sound. Grounding the signal circuit will provide a low voltage input to the PCM. The PCM should recognize this low voltage and indicate a high IAT temperature.
4. This test determines if the IAT sensor signal circuit is okay. If the scan tool does not indicate a high temperature, the IAT signal circuit is open.