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 the difference between the start-up coolant temperature and the start-up intake air temperature is more than a predetermined amount, this DTC sets. This DTC also sets if the current intake air temperature is more than a predetermined amount based on the start-up engine coolant temperature.
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
| • | DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0502, and P0562 are not set. |
| • | The engine is OFF for more than 8 hours. |
| • | The engine is operating. |
IAT Test 1
| - | The start-up engine coolant temperature is more than -20°C (-4°F). |
| - | The vehicle speed is more than 40 km/h (25 mph). |
| - | The mass air flow (MAF) sensor is more than 15 g/s. |
| - | The above conditions are met for more than 300 seconds. |
IAT Test 2
| - | The vehicle speed is more than 40 km/h (25 mph). |
| - | The mass air flow (MAF) sensor is more than 15 g/s. |
| - | The above conditions are met for more than 300 seconds. |
| • | DTC P0111 runs once an ignition cycle once the above conditions are met. |
Conditions for Setting the DTC
The ECM detects a 20°C (36°F) difference between the start-up engine coolant temperature and the start-up intake air temperature for more than 2 seconds.
Or
The ECM detects that the current intake air temperature is more than a predetermined amount based on the start-up engine coolant temperature for more than 2 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
| • | Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. |
| • | 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. |
| • | If the vehicle has set overnight, the IAT sensor and the ECT sensor values should display within 3°C (5°F). Refer to Temperature Versus Resistance . |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
This step isolates the condition. If the temperature changes, test for a condition in the low reference circuit. If the temperature remains the same test the signal circuit for a condition.
-
This step tests for excessive resistance in the IAT circuit.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector 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 DTC P0112, P0113, P0115, P0117, P0118, P0125, or P0128 also set? | -- | Go to Step 3 | |
3 |
Is the temperature more than the specified value? | 128°C (262°F) | Go to Step 7 | Go to Step 4 |
Is the temperature more than the specified value? | 128°C (262°F) | Go to Step 5 | Go to Step 6 | |
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 11 | Go to Step 8 | |
6 | 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 11 | Go to Step 8 |
7 | 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 11 | Go to Step 9 |
8 | 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 11 | Go to Step 10 |
9 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- |
10 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- |
11 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 12 |
12 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
