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 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
| • | No engine coolant temperature (ECT) sensor, mass air flow (MAF) sensor, or vehicle speed sensor (VSS) DTCs are present. |
| • | The engine has been running for more than 10 seconds. |
| • | The vehicle speed is more than 25 mph. |
Conditions for Setting the DTC
The IAT signal voltage intermittently indicates an intake air temperature of more than 135°C (275°F).
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:
| • | A faulty connection at the PCM--Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. Use a corresponding mating terminal to test for proper terminal tension. |
| • | Inspect the wiring harness for damage. If the harness appears to be OK, observe the IAT display on the scan tool while moving the 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 Versus Resistance . |
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||
2 | With a scan tool, select Diagnostic Trouble Codes (DTC). Does the scan tool indicate DTC P0112 also set? | -- | Go to DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage | |
3 | Test the signal circuit for an intermittent short to ground. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Diagnostic Aids | |
4 |
Does the DTC reset? | -- | System OK |
