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 powertrain control module (PCM) 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 PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an intermittent low IAT signal voltage, indicating a high temperature, DTC P1112 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1112 Intake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage
Conditions for Running the DTC
| • | DTC P0112 is not set. |
| • | The engine run time is more than 45 seconds. |
| • | The vehicle speed is more than 40 km/h (25 mph). |
| • | The ECT Sensor parameter is less than 125°C (257°F). |
| • | DTC P1112 runs continuously when the above conditions are met. |
Conditions for Setting the DTC
The PCM detects that the IAT Sensor parameter is more than 128°C (262°F) intermittently for a calibrated amount of time.
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
| • | An IAT sensor or PCM which is intermittently shorted, open, or skewed is possible, yet very unlikely. |
| • | A skewed sensor could result in poor driveability conditions. |
| • | If an intermittent condition is suspected, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls 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 | Observe the DTC information with a scan tool. Is DTC P0112 set? | -- | Go to DTC P0112 | Go to Step 3 |
3 | Test for an intermittent and for a poor connection at the intake air temperature (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 5 | Go to Step 4 |
4 | Test the IAT signal circuit between the IAT sensor and the powertrain control module (PCM) for an intermittent short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 5 | Go to Diagnostic Aids |
5 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 6 |
6 | 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 |
