P0111: Intake Air Temperature Sensor Range/Performance
P0111 means the engine computer decided the intake air temperature sensor reading does not match other temperature sensors, even though the signal itself is electrically normal. It is usually a minor fault with few noticeable symptoms, but it turns on the check engine light and can affect an emissions test.
You can keep driving
The data lists no limp mode for this code and usually no noticeable symptoms, so short-term driving is generally fine. Get it checked soon, because the light stays on, the fault is emissions-relevant, and a slightly changed idle, power or cold start is possible.
What it means
The intake air temperature (IAT) sensor measures how warm the air entering the engine is. 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 are thermistors (resistors whose value changes with temperature) on a 5 V circuit, and the signal voltage drops as the air gets hotter. P0111 is a plausibility fault. After the car has sat for a long time (Ford 6 hours, GM 8 hours), the computer compares the IAT reading at key-on with other temperature sensors such as coolant, cylinder head, charge air cooler or a second IAT sensor. They should all read about the same. GM flags the code at a deviation above about 25 °C and 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 pauses the test, and the fault must show up on two consecutive trips before the light comes on.
Likely causes
- Sensor drifting or stuck at one value (ageing, oil from crankcase ventilation)Very likely
A sensor that no longer follows the real air temperature will disagree with the other temperature sensors after a long soak.
- Contact resistance at the connector or wiringPossible
Extra resistance in a corroded or loose connection changes the signal voltage, so the reading is off.
- Faulty comparison sensor (coolant, second IAT, charge air cooler)Possible
The test compares sensors against each other, so a wrong reading from another sensor can trigger the code even if the IAT sensor is fine.
- Undetected preheater, heat soak or sensor near a heat sourceLess likely
Outside heat can make the intake sensor read warmer than the other sensors without any part being broken.
What you may notice
- Check engine light on
- Usually no noticeable symptoms
- Slightly changed idle, power or cold start possible
- Code often returns only after an overnight soak
What to check, cheapest first
- 1Read the code and any related codes (P0112, P0113, P0114 and others) and note whether other temperature sensor codes are present. · you can do it
- 2Inspect the sensor connector and wiring for corrosion, looseness, bent pins or damage, and reseat the connector. · you can do it
- 3Check whether the sensor, or the mass air flow sensor that contains it, is coated with oil from the crankcase ventilation, and whether it sits near a heat source. · you can do it
- 4With a scan tool after the car has sat for several hours, compare the intake air temperature with the coolant temperature and other temperature readings. They should be about equal. · mechanic
- 5Check the comparison sensors (coolant, second IAT, charge air cooler) and the sensor circuit for resistance problems. · mechanic
- 6Replace the faulty sensor, clear the code, and confirm it does not return after an overnight soak and two drive trips. · mechanic
Related codes
Frequently asked questions
Can I drive with P0111?+
Generally yes. The data lists no limp mode and usually no noticeable symptoms. Have it checked soon since the check engine light stays on.
Can a loose gas cap cause P0111?+
No. A gas cap affects fuel vapor codes, not this temperature comparison. P0111 comes from the sensor, its wiring, or a comparison sensor.
Will P0111 pass an emissions test?+
Probably not. The code is emissions-relevant and turns on the check engine light, so fix it and confirm it stays gone before testing.
Why does the code come back only after the car sits overnight?+
The main test runs at key-on after a long soak, when all temperature sensors should read the same. That is when a disagreement shows.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10