Circuit Description
The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The powertrain control module (PCM) applies 5 volts through a pull-up resistor to the IAT sensor. If the intake air is cold, the sensor resistance is high, and the PCM will monitor a high signal voltage on the IAT signal circuit. If the intake air is warm, the sensor resistance is lower causing the PCM to monitor a lower voltage. DTC P1112 will set when the PCM detects an intermittently low signal voltage on the IAT sensor signal circuit.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0117, P0118, P0125, P0128, P0501, P0502, P1114, or P1115 are not set. |
| • | The engine has been running for more than 10 seconds. |
| • | The vehicle speed is more than 40 km/h (25 mph). |
| • | the above conditions are present for at least 5 seconds. |
Conditions for Setting the DTC
| • | The IAT sensor indicates an IAT that is intermittently more than 135°C (275°F). |
| • | The conditions is present for up to 5 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. |
Diagnostic Aids
If the condition is intermittent, refer to Intermittent Conditions
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 | With a scan tool, select diagnostic trouble codes (DTC). Does the scan tool indicate DTC P0112 also set? | Go to DTC P0112 | Go to Step 3 |
3 | Test the IAT sensor signal circuit for an intermittent short to ground and repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections , and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 4 | Go to Diagnostic Aids |
4 |
Does the DTC run and pass? | Go to Step 5 | Go to Step 2 |
5 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK | |
