Circuit Description
The intake air temperature (IAT) sensor is a thermistor. The powertrain control module (PCM) 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 intermittent low voltage signals on the IAT sensor signal circuit.
Conditions for Running the DTC
| • | DTCs P0502 and P0503 are not set. |
| • | The vehicle speed is more than 3 km/h (2 mph). |
| • | The engine has been running for more than 100 seconds. |
Conditions for Setting the DTC
The IAT voltage is below a calibrated value for less than 1 second.
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | 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 non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
The IAT sensor indicates the temperature of the ambient air entering the throttle body. The scan tool displays the IAT as volts and temperature. The IAT temperature reading should be very close to the temperature of the outside air, and the IAT temperature should rise gradually as the engine warms up and the underhood temperature increases. An intermittent short to ground in the IAT sensor signal circuit could result in a DTC P1112. If a low IAT voltage reading is present, additional sensor circuit voltage codes could be set. Refer to any non-intermittent DTCs that are set. Also, a sensor may become skewed or mis-scaled. The Temperature vs. Resistance value table will help to detect a skewed sensor. Refer to Temperature Versus 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 Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference:
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Important: Be sure to use the same diagnostic test equipment for all measurements. | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Is the IAT sensor temperature more than the specified value? | 139°C (282°F) | Go to DTC P0112 | Go to Step 3 | |
3 |
Did you find a problem? | -- | Go to Step 6 | Go to Step 4 |
4 |
Did you find a problem? | -- | Go to Step 6 | Go to Step 5 |
5 |
Did the temperature fluctuate? | -- | Go to Step 6 | Go to Diagnostic Aids |
6 | Repair the circuit as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 7 | -- |
7 |
Does the scan tool indicate the diagnostic Passed? | -- | Go to Step 8 | Go to Step 2 |
8 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
