P1112

CIRCUIT DESCRIPTION
The Intake Air Temperature (IAT) sensor contains a semiconductor device, a thermistor, which changes the resistance based on the temperature. The IAT sensor has a signal circuit and a low reference circuit. The Powertrain Control Module (PCM) applies 5.0 volts on the signal circuit to the sensor. The PCM monitors the changes in this voltage caused by changes in the resistance of the sensor in order to determine intake air temperature.

When the intake air is cold, the sensor or thermistor resistance is high. The PCM signal voltage only pulls down a small amount through the sensor to a ground. Therefore, the PCM senses a high signal voltage or low temperature. When the intake air is warm, the sensor resistance is low. The signal voltage pulls down a large amount. Therefore, the PCM senses a low signal voltage, or a high temperature.

When the PCM senses a signal voltage lower than the normal operating range of the sensor, this DTC sets.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0102, P0103, P0117, P0118, P0500, P0502, or P0503 are not set.
^ The Engine Coolant Temperature (ECT) is less than 135°C (275°F).
^ The engine run time is more than 30 seconds.
^ The vehicle speed is more than 40 km/h (25 mph).

CONDITIONS FOR SETTING THE DTC
^ The Intake Air Temperature (IAT) is more than 139°C (282°F).
^ The intermittent condition exists for a total of 5.5 seconds during a 100-second 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.
^ Use a scan tool in order to clear the DTC.

DIAGNOSTIC AIDS
If the engine sat overnight, the ECT and the IAT values should display within a few degrees of each other. If the temperatures are not within 3°C (5°F), refer to Temperature vs Resistance. Temperature VS Resistance

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

TEST DESCRIPTION

Steps 1-10:

The numbers below refer to the step numbers on the diagnostic table.
2. If DTC P0112 failed this ignition, a hard failure is present. When a hard failure is present, both the hard and the intermittent DTCs set.

For any test that requires probing the PCM or component harness connectors, use the connector test adapter kit. Using this kit prevents any damage to the harness connector terminals.
3. This step inspects for the proper connections.
4. This step inspects the wiring harness.
5. Using the Freeze Frame/Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature etc., that you observed. This will isolate when the DTC failed.