P1112

DTC P1112

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 intermittent 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 P1112 Intake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage

Conditions for Running the DTC

* DTC P0502 is not set.

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

* The engine run time is more than 120 seconds.

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

Conditions for Setting the DTC

The ECM detects that the IAT is more than 149°C (300°F) intermittently for a total of 10 seconds during a 20 second time period.

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

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

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