Circuit Description
The intake air temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The powertrain control module (PCM) supplies 5 volts to the IAT signal circuit and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an excessively high IAT signal voltage, indicating a low temperature, DTC P0113 sets.
Conditions for Running the DTC
| • | DTCs P0116, P0117, P0118, P0125, P0128, P0502, or P0503 are not set. |
| • | The engine run time is more than 10 seconds. |
| • | The vehicle speed sensor indicates that vehicle speed is less than 80 km/h (48 mph). |
| • | The mass air flow is less than 12 g/s. |
| • | The engine coolant temperature is more than 60°C (140°F). |
Conditions for Setting the DTC
The IAT is less than -39°C (-38°F) for more than 1 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. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | When the vehicle is at ambient temperature the IAT sensor and ECT sensor temperatures should be relatively close to each other. Refer to Temperature Versus Resistance . |
| • | If a short to a separate 5-volt source occurs this DTC may set. If this condition exists, a continuity test to all other PCM 5-volt reference circuits will be necessary. |
| • | If an intermittent condition is suspected, refer to Intermittent Conditions . |
Test Description
The number below refer to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls ? | -- | Go to Step 2 | |
2 |
Is the IAT sensor temperature less than the specified value? | -38°C (-36°F) | Go to Step 4 | Go to Step 3 |
3 |
Does the DTC reset? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Does the DMM voltage measure more than the specified value? | 5 V | Go to Step 5 | Go to Step 6 |
5 |
Important: The sensor may be damaged if the circuit is shorted to a voltage source. Did you find and correct the condition? | -- | Go to Step 14 | Go to Diagnostic Aids |
Is the IAT sensor temperature more than the specified value? | 128°C (262°F) | Go to Step 10 | Go to Step 7 | |
7 |
Is the IAT sensor temperature more than the specified value? | 128°C (262°F) | Go to Step 9 | Go to Step 8 |
8 | Test the signal circuit of the IAT sensor for an open circuit or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 |
9 | Test the IAT sensor low reference circuit for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11 |
10 |
Important: If a short to a separate voltage source occurs, this DTC may set. The short may damage the IAT sensor. If this condition exists, a continuity test to all other PCM circuits will be necessary to diagnose the specific fault. Inspect for poor connections at the harness connector of the IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12 |
11 |
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13 |
12 | Replace the IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Does the DTC run and pass? | -- | Go to Step 15 | Go to Diagnostic Aids |
15 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
