P0112

DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Input A




Circuit Description
The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The powertrain control module (PCM) applies 5 volts through a pull-up resistor to the IAT sensor. When the intake air is cold, the sensor resistance is high and the PCM will monitor a high signal voltage on the IAT signal circuit. If the intake air is warm, the sensor resistance is lower, causing the PCM to monitor a lower voltage. Diagnostic Trouble Code P0112 will set when the PCM detects an excessively low signal voltage (short to ground) on the intake air temperature sensor signal circuit. DTC P0112 is a Type A Code.

Conditions for Setting the DTC
- The engine has been running for over 2 minutes.
- Vehicle speed is greater than 48 kph (30 mph).
- IAT signal voltage less than 0.10 volts for a total of 12.5 seconds over a 25-second period of time. The above conditions are met for at least 2 seconds.

Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) the first time the fault is detected.
- The PCM will use a default IAT valve based on PCM inputs and engine run time.
- The PCM will store conditions which were present when the DTC was set as Freeze Frame and in the Failure Records data.

Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history DTC P0112 will clear after 40 consecutive warm-up cycles have occurred without a fault. DTC P0112 can be cleared by using the Scan Tool's "Clear Info" function.

Diagnostic Aids
Check for the following conditions:
- Poor connection at PCM - 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 shorts to ground, shorts to battery and open circuits. If the harness appears to be OK, observe the IAT display on the Scan Tool while moving connectors and wiring harnesses related to the IAT sensor. A change in the IAT display will indicate the location of the fault.

If Diagnostic Trouble Code P0112 cannot be duplicated, the information included in the Failure Records data can be useful in determining vehicle mileage since the Diagnostic Trouble Code was last set.

Steps 1 - 7:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
2. Verifies that the fault is present.
3. If Diagnostic Trouble Code P0112 can be repeated only by duplicating the Failure Records condition, refer to the Temperature vs. Resistance Value table.

The table may be used to test the IAT sensor at various temperatures to evaluate the possibility of a "shifted" sensor that may be stored above or below a certain temperature. If this is the case, replace the IAT sensor. If the IAT sensor appears to be OK, the fault is intermittent; refer to Diagnostic Aids.




Intake Air Temperature Sensor