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 engine control module (ECM) 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 ECM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the IAT signal circuit. If the ECM detects an excessively high IAT signal voltage, indicating a low temperature, DTC P1111 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage
Conditions for Running the DTC
| • | DTCs P0112 and P0113 are not set. |
| • | The engine metal over temperature protection (EMOP) is not active. |
| • | The ignition is ON. |
| OR |
| • | The engine is running for more than 2 minutes. |
| • | DTC P1111 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
The IAT sensor parameter is less than -39°C (-38°F) for more than 3.2 seconds.
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. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | Are DTCs P0641 or P0651 set? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 |
3 | Observe the IAT Sensor parameter with a scan tool. Is the IAT Sensor parameter less than the specified value? | -39°C (-38°F) | Go to Step 5 | Go to Step 4 |
4 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Inducing Intermittent Fault Conditions in Wiring Systems and Intermittent Conditions |
5 |
Is the voltage more than the specified value? | 5.2 V | Go to Step 6 | Go to Step 7 |
6 |
Important: The sensor may be damaged if the circuit is shorted to a voltage source. Test the IAT signal circuit for an intermittent short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 |
Is the IAT sensor parameter more than the specified value? | 128°C (262°F) | Go to Step 11 | Go to Step 8 | |
8 |
Is the IAT Sensor parameter more than the specified value? | 128°C (262°F) | Go to Step 10 | Go to Step 9 |
9 | Test the IAT signal circuit for an intermittent open circuit or intermittent high resistance. Refer to Inducing Intermittent Fault Conditions , Circuit Testing , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 |
10 | Test the IAT low reference circuit for an intermittent open circuit or intermittent high resistance. Refer to Circuit Testing , Inducing Intermittent Fault Conditions , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 |
11 | Test the IAT signal circuit for an intermittent short to any 5-volt reference circuit. Refer to Circuit Testing , Inducing Intermittent Fault Conditions , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 12 |
12 |
Important: The sensor may be damaged if the circuit is shorted to a voltage source. Test for an intermittent and for a poor connection at the MAF/IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections , Inducing Intermittent Fault Conditions , and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 |
13 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections , Inducing Intermittent Fault Conditions , and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 |
14 | Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- |
15 | Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 16 | -- |
16 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 17 |
17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
