Circuit Description
The intake air temperature (IAT) sensor is a variable resistor that measures the temperature of the air entering the engine. The IAT sensor has a signal circuit and a low reference circuit. The engine control module (ECM) supplies 5 volts to the IAT signal circuit and a ground for the IAT low reference circuit. If the ECM detects that the IAT signal voltage is not changing due to engine running conditions, this DTC sets.
The following table illustrates the difference between temperature, resistance, and voltage:
IAT | IAT Resistance | IAT Signal Voltage |
|---|---|---|
Cold | High | High |
Warm | Low | Low |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0111 Intake Air Temperature (IAT) Sensor Performance
Conditions for Running the DTC
| • | The engine is running for more than 5 minutes. |
| • | The engine coolant temperature is more 74°C (165°F). |
| • | The engine coolant temperature increase from startup is more than 40°C (104°F). |
| • | The vehicle has been driven for more than 7 kilometers (4.2 miles). |
| • | The vehicle speed is more than 5 Km/h (3 mph) for more than 12 seconds. |
| • | This DTC runs once per ignition cycle once the above conditions are met. |
Conditions for Setting the DTC
The ECM detects that the actual IAT has not changed more than 1.5°C (35°F) from the startup IAT for more than 10 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
| • | Test the IAT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a driveability condition. |
| • | A high resistance on the IAT signal circuit or the IAT low reference circuit may not set a DTC. Refer to Circuit Testing in Wiring Systems. |
| • | If the vehicle has set overnight, the IAT sensor and the engine coolant temperature (ECT) sensor values should display within 3°C (5°F). Refer to Temperature Versus Resistance . |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connect End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 |
Is the temperature at the specified value? | 120°C (248°F) | Go to Step 6 | Go to Step 3 |
3 |
Is the temperature at the specified value? | 120°C (248°F) | Go to Step 4 | Go to Step 5 |
4 | Test the low reference circuit of the IAT sensor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
5 | Test the signal circuit of the IAT sensor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
6 | Test for shorted terminals and poor connections at 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 10 | Go to Step 8 |
7 | Test for shorted terminals and poor connections at the ECM. 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 10 | Go to Step 9 |
8 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
9 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 11 |
11 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
