P0111Powertrain
Powertrain · SAE
IAT Sensor Range/Performance
Meaning
The intake air temperature (IAT) sensor reads implausible values: temperature does not change from the engine-off value after a cold soak and restart, is inconsistent with coolant temperature at cold start, or falls outside physically possible limits. The IAT is typically an NTC thermistor.
Common causes
- Failed NTC sensor (resistance stuck at one value)
- Contamination of the sensor element
- Intermittent wiring fault causing random readings
- Inconsistency detected by comparison with coolant temperature sensor at cold start
Symptoms
- MIL illuminated
- Incorrect cold-start fuel enrichment
- Possible lean or rich running at start-up
- Slight increase in fuel consumption
Severity
Low-to-moderate severity: primarily affects cold-start enrichment and ignition advance accuracy.
What to do
- Measure IAT sensor resistance and compare to the temperature-resistance chart (NTC decreases resistance with rising temperature)
- Compare IAT and ECT readings at cold start (should be near equal after an overnight soak)
- Check wiring for intermittent fault
- Replace sensor if resistance is out of specification