P1111

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Steps 5 - 8:

DTC P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage




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 P1111 will set when the PCM intermittently detects an excessively high signal voltage on the intake air temperature sensor signal circuit. DTC P1111 is a type D code.

Conditions for Setting the DTC
The engine has been running for over 4 minutes.
- Vehicle speed is less than 32 km/h (20 mph).
- Engine coolant temperature is above 60 °C (140 °F).
- Calculated air flow is less than 20 g/second.
- IAT signal voltage indicates an intake air temperature intermittently less than -39 °C (-38 °F) (4.94 volts) for approximately 2.5 seconds over a 25 - second period of time.

Action Taken When the DTC Sets
- The PCM will substitute a default value for intake air temperature.
- The PCM will store conditions which were present when the Diagnostic Trouble Code set as Failure Records data only. This information will not be stored as Freeze Frame data.
- Diagnostic Trouble Code P1111 does not illuminate the MIL.

Conditions for Clearing the DTC
- A history DTC P1111 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- Diagnostic Trouble Code P1111 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 positive, and open circuits. If the harness appears to be OK, observe the IAT display on the Tech 2 while moving connectors and wiring harnesses related to the IAT sensor. A change in the IAT display will indicate the location of the fault.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the Diagnostic Trouble Code to be set occurs. This may assist in diagnosing the condition.




Intake Air Temperature Sensor