P0112

DTC P0112

Circuit Description

The intake air temperature (IAT) sensor is a variable resistor. The AT 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 excessively low IAT signal voltage, indicating a high temperature, DTC P0112 sets.

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





DTC Descriptors

This diagnostic procedure supports the following DTC. DTC P0112 AT Sensor Circuit Low Voltage


Conditions for Running the DTC

- DTCs P0102, P0103, P0117, P0118, are not set.

- The engine is operating for more than 30 seconds.

- The vehicle is less than 40 km/h (25 mph).


Conditions for Setting the DTC

- The AT is more than 139°C (282°F).

- The condition exists for more than 19 seconds.

Action Taken When the DTC Sets

- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and tails.

- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the 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

DTC P0112 Steps 1-11:

- When the vehicle is at ambient temperature the IAT sensor and ECT sensor temperatures should be relatively close to each other.

- If an intermittent condition is suspected, refer to Intermittent Conditions.Symptom Related Diagnostic Procedures