P1111

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Steps 4 - 9:

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

Conditions for Setting the DTC
- The engine has been running for over 4 minutes.
- Vehicle speed is less than 20 mph (32 kph).
- Engine coolant temperature is above 60 °C (140 °F).
- Mass air flow is less than 20 g/second.
- IAT signal voltage indicates and intake air temperature intermittently less than -39 °C (-38 °F) (about 5 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 DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.
- DTC P1111 does not illuminate the MIL.

Conditions for Clearing the MIL/DTC
- A history DTC P1111 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- DTC P1111 can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.
- DTC P1111 can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

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. 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 fault.

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.




Intake Air Temperature Sensor