P0111

Circuit Description

The Intake Air Temperature sensor is a thermistor, or variable resistor, that varies resistance based on temperature. Low temperature will result in a high signal voltage. This diagnostic test monitors Intake Air Temperature (IAT) sensor voltage. If the PCM detects a large change in sensor signal voltage in a 0.25 second period, DTC P0111 will set.

Conditions for Running the DTC

2 seconds have passed since key ON.

Conditions for Setting the DTC

Intake Air Temperature (IAT) sensor voltage has changed 0.3 volts in 0.25 second.

Action Taken When the DTC Sets

^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ No message will be displayed.
^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
^ A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
^ Use a scan tool to clear DTCs.
^ Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids

Artificially changing the temperature of the IAT can be done by careful warming with a heat gun or by cooling the IAT (refrigerator, etc.) then allowing it to warm.

If fault is not present perform Powertrain Ground Check and also review Failure Rec. to determine conditions under which and how long ago the DTC set. Component Tests and General Diagnostics

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

3. Checking DTC P0111 snapshot value to determine if an intermittent high resistance caused the DTC to set.
4. An intermittent high resistance can be caused by an open in the IAT Sensor ground circuit or the IAT Sensor Signal circuit.
6. An intermittent low resistance can be caused by a short to ground on the IAT Sensor Signal circuit.
7. Checking the IAT sensor's ability to read a full range of temperatures.