P1111

P1111 Intake Air Temperature Intermittent High Voltage




Circuit Description
The Intake Air Temperature (I AT) sensor is a thermistor which measures the temperature of the air entering the engine. The powertrain control module (PCM)/engine control module (ECM) applies 5 volts through a pull-up resistor to the IAT sensor. When the intake air is cold, the resistance is high, and the PCM/ECM 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/ECM to monitor a lower voltage. DTC P1111 will set when the PCM/ECM detects an excessively high signal voltage on the intake air temperature sensor signal circuit.

Conditions for Setting the DTC
- DTC P0502 is not set
- Engine has been running for over 120 seconds.
- Vehicle speed is less than 70 mph (113 kph).
- Calculated air flow is less than 30 g/second.
- Engine Coolant Temperature (ECT) is above 18 °F (-8 °C).

Action Taken When the DTC Sets
- The PCM/ECM will substitute a default value for IAT.
- The PCM/ECM 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.
- The Malfunction Indicator Lamp (MIL) will not illuminate.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC can be cleared by using the scan tool.

Diagnostic Aids
Check for the following conditions:
- Poor connection at the PCM/ECM. 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 Fail 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.
- Use the Temperature vs. Resistance Values table to evaluate the possibility of a skewed sensor. Refer to "Temperature vs. Resistance".

Intake Air Temperature Sensor:

Intake Air Temperature Sensor

Step 1 - 7:

Step 8 - 11:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.