P0111: OBD-II code P0111 means the intake air temperature (IAT) sensor signal is present but implausible — it doesn't track ambient temperature changes as expected.

Symptoms

• Check engine light is on; engine may run slightly rich or lean depending on the sensor's bias.
• Minor fuel economy loss because the PCM's fuel calculation is based on inaccurate air temperature.
• Symptoms are often subtle — many drivers only notice the code when they scan the vehicle for another issue.

Common causes

• A drifting or ageing IAT sensor whose response no longer matches manufacturer spec.
• Contamination (oil, dust) on the sensor element damping its response to temperature changes.
• Wiring resistance or a corroded connector biasing the reading away from truth.

What to do?

Compare live IAT vs actual ambient temperature at cold start — the two should be within a few degrees. Backprobe the signal with a DMM. Replace the sensor if the drift is confirmed. Clean or replace the connector if resistance is present.