P0111
Intake Air Temperature Sensor 1 Circuit Range/Performance Bank 1
The engine computer thinks the intake air temperature signal does not make sense for the way the engine is running. That usually means the sensor is biased, the wiring or connector has extra resistance or poor contact, or the intake temperature signal inside the MAF assembly is not reacting correctly. The result can be hard starting, rough running, poor fuel economy, or hesitation.
- SEV
- 3/5
- DRIVE
- CAUTION
- DIY
- $15-$120
- SHOP
- $120-$400
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Faulty or biased intake air temperature sensor
- Corroded, loose, or damaged intake air temperature sensor wiring or connector
- Mass air flow sensor assembly fault on vehicles with an integrated IAT sensor
Typical repair cost
DIY usually runs $15-$120. Typical shop repair lands around $120-$400, depending on the root cause.
01 / Definition
P0111 sets when the PCM sees an intake air temperature sensor signal that is out of the expected range or is not changing the way it should for current operating conditions. On many vehicles the IAT sensor is a thermistor, and the PCM compares that reading with ambient conditions, engine load, and sometimes MAF or MAP data. A biased sensor, poor connector contact, wiring fault, or an integrated MAF and IAT assembly problem can all make the temperature reading look inaccurate enough to trigger the code.
02 / Drive status
With caution. You can often drive short distances, but the engine may run rich or lean, hesitate, or use more fuel than normal. Fix it soon, especially if cold starts are poor, the engine is stalling, or related MAF or fuel-trim codes are present.
03 / Symptoms
- Check engine light on
- Hard starting, especially when cold
- Rough idle
- Hesitation during acceleration
- Poor fuel economy
- Reduced engine performance
- Rich or lean fuel-trim problems
04 / Causes
| 1 | Faulty or biased intake air temperature sensor | high |
|---|---|---|
| 2 | Corroded, loose, or damaged intake air temperature sensor wiring or connector | high |
| 3 | Mass air flow sensor assembly fault on vehicles with an integrated IAT sensor | medium |
| 4 | Restricted, disconnected, or heat-soaked intake path causing implausible temperature data | medium |
| 5 | PCM software or reference-calculation issue | low |
05 / Diagnostic sequence
- 01Scan for related intake air temperature, MAF, MAP, or fuel-trim codes before treating P0111 as a sensor-only problem.
- 02Compare intake air temperature on a cold engine to ambient temperature and note whether the reading is already implausible before moving parts or unplugging connectors.
- 03Inspect the IAT sensor connector and harness for corrosion, loose terminals, spread pins, damaged insulation, or poor previous repairs.
- 04Check live data while the engine warms up and while airflow changes to confirm whether the intake temperature signal responds smoothly and reasonably.
- 05If the IAT is integrated into the MAF housing, inspect the air filter, intake duct, and the MAF assembly for dirt, restriction, or connector issues.
- 06Measure sensor resistance or signal voltage and compare it with service information for the current temperature.
- 07Repair the wiring or replace the failed sensor or MAF assembly as indicated, then clear the code and road test to confirm the reading now tracks normally.
06 / Repairs
| 1 | Repair corroded or loose terminals, damaged wiring, or poor connector fit at the intake air temperature sensor circuit | $10-$100 |
|---|---|---|
| 2 | Replace the intake air temperature sensor if resistance or signal testing shows it is biased or slow to respond | $15-$80 |
| 3 | Replace the MAF assembly on platforms where the IAT sensor is built into the housing and the unit fails testing | $80-$250 |
| 4 | Repair intake duct restrictions or poor air filter installation that are distorting the temperature reading | $15-$60 |
| 5 | Update PCM software or continue circuit diagnosis only after the sensor and intake hardware test good | $100-$250 |
07 / Related codes
08 / FAQ
What does P0111 mean?
It means the intake air temperature signal does not agree with what the PCM expects for current engine conditions. The reading may be biased, slow to react, or inconsistent with other sensor data.
Can a bad MAF sensor cause P0111?
Yes. On vehicles where the intake air temperature sensor is built into the MAF housing, a faulty MAF assembly can trigger P0111.
Will P0111 cause poor fuel economy?
Yes. Incorrect intake temperature data can cause the PCM to miscalculate fuel delivery, especially during startup and changing load conditions.
Should I replace the IAT sensor first?
Not before checking the connector, wiring, and whether the sensor is integrated into the MAF housing. A connection problem can create the same code.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.