Circuit Description
The Intake Air Temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The PCM applies 5.0 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 P1112 will set when the PCM detects an intermittently low signal voltage on the intake air temperature sensor signal circuit.
Conditions for Running the DTC
| • | The engine has been running for over 10 seconds. |
| • | Vehicle speed is greater than 25 mph. |
Conditions for Setting the DTC
| • | The IAT sensor indicates an intake air temperature intermittently greater than 135°C (275°F). |
| • | The conditions is present for up to 5 seconds. |
Action Taken When the DTC Sets
The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.
Conditions for Clearing the MIL/DTC
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The history DTC clears after 40 malfunction free warm-up cycles. |
| • | The PCM receives a clear code command from the scan tool. |
Diagnostic Aids
Check for the following conditions:
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Poor terminal connection. |
| Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Intermittents and Poor Connections Diagnosis , and Connector Repairs Wiring Systems. |
| • | Damaged harness. |
| Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems. |
| • | Inspect the PCM and the engine grounds for clean and secure connections. |
If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table:
-
Verifies that the fault is present.
-
If DTC P1112 can be repeated only by duplicating the Fail Records conditions. Refer to the Temperature Versus Resistance table. The chart may be used to test the IAT sensor at various temperatures 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.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain on Board Diagnostic System Check performed? | -- | ||
Select DTC info, Last Test Fail and note any other DTCs set. Is DTC P0112 also set? | -- | Go to DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage | ||
Was a problem found? | -- | Go to Diagnostic Aids | ||
4 |
Does scan tool indicate DTC P1112 failed? | -- | System OK |
