P0112

Intake Air Temperature (IAT) Sensor Circuit:

Circuit Description
The Intake Air Temperature (IAT) sensor is a thermistor which controls the signal voltage to the PCM. The PCM supplies a 5V reference and a ground to the sensor When the air is cold the resistance will be high. Whenever the intake air is warm, the resistance will be low.

Conditions For Setting The DTC
- The engine run time is greater than 320 seconds.
- The vehicle speed sensor indicates that vehicle speed is greater than 15 mph (24km/h).
- The IAT sensor signal voltage indicates that the intake air temperature is greater than 128°C (262°F).

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
- The PCM will default to 60°C for intake air temperature. The scan tool will not show the defaulted value.

Conditions for Clearing the MIL/DTC
- The MIL will turn "OFF" after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- DTCs can be cleared by using a scan tool.

Diagnostic Aids
- When the vehicle is at ambient temperature, compare the IAT sensor to the ECT sensor. The IAT sensor and the ECT sensor should be relatively close to each other.

IAT sensor Temperature Vs Resistance Values:

- Use the "Temperature Vs Resistance Values" Table to evaluate the possibility of a skewed sensor.

DTC PO112 - Intake Air Temperature (IAT) Sensor Circuit Low Voltage:

Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
1. The OBD System Check prompts the Technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool it applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
8. Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Replacement PCM must be reprogrammed. Refer to the latest Techline information for programming procedures.