P0112

DTC P0112

Circuit Description

The intake air temperature (IAT) sensor is a variable resistor that measures the temperature of the air entering the engine. The IAT sensor has a signal circuit and a low reference circuit. The engine control module (ECM) supplies 5 volts to the IAT signal circuit and a ground for the IAT low reference circuit. If the ECM detects an excessively low IAT signal voltage, which is a high temperature indication, this DTC sets.

The following table illustrates the difference between temperature, resistance, and voltage:






DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage

Conditions for Running the DTC

* DTC P0502 is not set.

* The engine run time is more than 120 seconds.

* The vehicle speed is more than 50 km/h (31 mph).

* This DTC runs continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects that the IAT sensor is more than 149°C (300°F) for more than 10 seconds.

Action Taken When the DTC Sets

* The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

* The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC

* The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

* 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 emission related diagnostic.

* Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

* Test the IAT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a driveability condition.

* If the engine has sat overnight, the IAT sensor and the engine coolant temperature (ECT) sensor values should display within 3°C (5°F). Refer to Temperature Versus Resistance Temperature Versus Resistance.

* A high resistance on either the IAT sensor signal circuit or the IAT sensor low reference circuit may not set a DTC. Refer to Circuit Testing Circuit Testing in Wiring Systems.

* For an intermittent condition, refer to Intermittent Conditions Intermittent Conditions.