P0112

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. DTC P0112 will set when the PCM detects an excessively low signal voltage on the intake air temperature sensor signal circuit.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0502 and P0503 are not set.
^ The engine has been running for more than 10 seconds.
^ The vehicle speed is more than 40 km/h (25 mph).

CONDITIONS FOR SETTING THE DTC
^ The IAT signal voltage indicates an intake air temperature that is more than 135°C (275°F).
^ The above conditions are present for at least 20 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ First failure:
- The MIL is not turned ON.
- A DTC is stored in memory under Failed Last Test.
- The Failure Records are stored.
^ Second consecutive drive cycle with a failure:
- The MIL is turned ON.
- A DTC is stored in memory under history.
- The Freeze Frame data is stored.
- The Failure Records are stored.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after the third consecutive trip the diagnostic has run and passed.
^ The history DTC will clear if the fault conditions have not been detected for 40 warm-up cycles.
^ A scan tool can be used to clear DTC information.

DIAGNOSTIC AIDS
Check for the following conditions:
^ Poor connection at the PCM-inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ A damaged harness-Inspect the wiring harness for damage. 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 malfunction.
^ A skewed or mis-scaled IAT sensor-Refer to Temperature vs Resistance.

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

TEST DESCRIPTION

Steps 1-9:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that the malfunction is present.
3. If DTC P0112 can be repeated only by duplicating the Failure Records conditions. The table may be used in order to test the IAT sensor at various temperatures in order to evaluate the possibility of a shifted sensor that may be shorted above or below a certain temperature. If this is the case, replace the IAT sensor.

If the IAT sensor appears to be OK, the malfunction is intermittent, refer to Diagnostic Aids.
7. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.