Circuit Description
The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The engine control module (ECM) applies 5 volts through a pull-up resistor to the IAT sensor. When the intake air is cold, the resistance is high, and the ECM will monitor a high signal voltage on the IAT signal circuit. If the intake air is warm, the sensor resistance is lower causing the ECM to monitor a lower voltage. DTC P1111 will set when the ECM detects an intermittent high signal voltage in the intake air temperature sensor signal circuit or sensor.
Conditions for Setting the DTC
| • | The IAT is less than -38°C (-36°F). |
| • | DTC P0502 is not set. |
| • | The engine has been running for over 120 seconds. |
| • | The vehicle speed is less than 25 km/h (16 mph). |
| • | Calculated air flow is less than 15 g/second. |
| • | The engine coolant temperature (ECT) is above 70°C (158°F). |
Action Taken When the DTC Sets
| • | The ECM will substitute a default value for IAT. |
| • | The ECM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
Inspect for the following conditions:
| • | A poor connection at the ECM--Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal-to-wire connection. |
| • | A damaged harness--Inspect the wiring harness for damage. If the harness appears to be OK, observe the IAT display on the scan tool while moving connectors and wiring harnesses related to the IAT sensor. A change in the IAT display will indicate the location of the fault. |
| • | Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition. |
| • | Use the Temperature vs. Resistance Values table to evaluate the possibility of a skewed sensor. Refer to Temperature Versus Resistance . |
Step | Action | Yes | No |
|---|---|---|---|
1 | Perform an On-Board Diagnostic System Check. Was the check performed? | Go to Step 2 | |
2 |
Is DTC P0113 set? | Go to applicable DTC table | Go to Step 3 |
3 | Is DTC P1115 also set? | Go to Step 7 | Go to Step 4 |
4 | Inspect for a poor sensor ground circuit terminal 2 at the intake air temperature (IAT) sensor and repair as needed. Did you find and correct the condition? | Go to Step 9 | Go to Step 5 |
5 | Inspect for a poor sensor signal circuit between terminal 1 of the IAT sensor and terminal A23 of the engine control module (ECM) for an intermittent open and repair as needed. Did you find and correct the condition? | Go to Step 9 | Go to Step 6 |
6 | Inspect for sensor signal circuit between terminal 1 of the IAT sensor and terminal A23 of the ECM for an intermittent short to voltage and repair as needed. Did you find and correct the condition? | Go to Step 9 | Go to Step 7 |
7 | Inspect for poor sensor ground circuit terminal A32 at the ECM and repair as needed. Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
8 | Inspect for an intermittent open or a faulty splice in the sensor ground circuit and repair as needed. Did you find and correct the condition? | Go to Step 10 | Go to Diagnostic Aids |
9 |
Does the scan tool indicate that this diagnostic has run and passed? | Go to Step 10 | Go to Step 2 |
10 | Are any DTCs displayed that have not been diagnosed? | Go to applicable DTC table | System OK |
