P0111: Intake Air Temperature Sensor 1 Circuit Range/Performance Bank 1

What does P0111 mean?

Intake air temperature sensor 1 is the first air temperature sensor in the intake path; depending on the vehicle it is built into the mass air flow sensor, mounted near the air filter or, on some naturally aspirated GM engines, fitted in the intake manifold. Most versions are NTC thermistors in a 5 V divider: the hotter the air, the lower the signal voltage. P0111 is a plausibility fault: the signal is electrically valid but does not fit. The usual test runs at key-on after a long soak (Ford 6 h, GM 8 h): the intake air sensor is compared with other temperature sensors such as coolant, cylinder head, charge air cooler or IAT2, which should all read about the same. GM flags it above about 25 °C deviation, Ford above about 17 °C; Ford first confirms with a drive above 40 mph because sunshine can warm a sensor, and also sets P0111 if the air reads over 66 °C while driving. A detected block heater suspends the test. Two consecutive trips are needed.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Usually no noticeable symptoms
• Slightly changed idle, power or cold start possible
• Code often returns only after an overnight soak

Common causes

• High Sensor drifting or stuck at one value (ageing, oil from crankcase ventilation)
• Medium Contact resistance at connector or wiring distorts the reading
• Medium Comparison sensor (coolant, IAT2, charge air cooler) wrong
• Low Undetected preheater, heat soak or sensor mounted near a heat source

Likelihood is a general estimate across vehicles; your make and model may differ.