P0112

DTC P0112

Circuit Description
The intake air temperature (IAT) sensor is fitted between the air cleaner and turbocharger. It is internal to mass air flow (MAF) sensor. The 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 low IAT signal voltage, indicating a high temperature, this DTC will set.

Condition for Running the DTC
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.

Condition for Setting the DTC
- The ECM detects that the IAT signal voltage is less than 0.1 volts.

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
- The ECM uses an IAT substitution of 77 °F (25 °C) when the DTC is set.
- The ECM uses an IAT substitution of -20 °F (-29 °C) for engine starting.
- The ECM uses an IAT substitution of 77 °F (25 °C) for engine running.

Condition for Clearing the DTC
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
- When the vehicle is at ambient temperature the IAT sensor and engine coolant temperature (ECT) sensor temperature should be relatively close to each other.
- Use the Temperature vs. Resistance table to test the IAT sensor at various temperature levels to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns. Refer to Temperature vs. Resistance.

If an intermittent condition is suspected, the following may cause an intermittent:
- Misrouted harness.
- Rubbed through wire insulation.
- Broken wire inside the insulation.

Check for the following conditions:
- Poor connection at ECM: Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged harness: Inspect the wiring harness for damage. If the harness appears to be OK, observe the "IAT Sensor" display on the scan tool with the engine running while moving connectors and wiring harness related to the sensor. A change in the display will indicate the location of the fault.

NOTE: The MAF sensor is heated and as a result the IAT sensor may indicate a higher than normal intake air temperature.

DTC P0112

Schematic Reference: Engine Controls Schematics