P0111
Intake Air Temperature Circuit Range/Performance Problem Bank 1P0111 is a generic OBD-II powertrain diagnostic trouble code: Intake Air Temperature Circuit Range/Performance Problem Bank 1. It is logged by the engine control unit when the air/maf monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0111 means
P0111 is stored when the powertrain control module (PCM) detects that the signal from the Intake Air Temperature (IAT) sensor is behaving erratically or producing a reading that is implausible given the engine's current operating conditions. Unlike P0112 and P0113, which flag fixed out-of-range voltages, P0111 is a performance code — it fires when the sensor's output changes too rapidly, too slowly, or in a way that conflicts with correlated data such as the engine coolant temperature (ECT) sensor or a reference ambient temperature model.
The IAT sensor is a Negative Temperature Coefficient (NTC) thermistor whose resistance decreases as temperature rises. The PCM supplies a 5 V reference; the voltage seen at the PCM input falls as temperature increases (approximately 4.5 V at −40 °C and 0.5 V at 100 °C). The PCM uses IAT data to calculate air density for fuelling corrections, ignition advance, boost target (on turbocharged engines), and cold-start enrichment. A faulty reading therefore degrades fuel economy, power output, and emissions.
A common real-world trigger on turbocharged petrol and diesel engines is an IAT sensor that has been contaminated with oil vapour from the crankcase ventilation (CCV) system, causing erratic resistance values. Intermittent connector corrosion due to the sensor's position in the intake tract — often subject to heat cycles and condensation — is another frequent cause. On MAF sensors with an integrated IAT element, a failed MAF can set P0111 alongside MAF codes.
The code typically sets after a full warm-up cycle where the PCM compares the IAT reading against the ECT reading and expected ambient temperature model. A significant, sustained discrepancy triggers the fault. Resolving P0111 promptly is important on calibrated ECUs because fuelling and boost strategies rely on accurate inlet temperature data.
Common causes
Most-frequently reported root causes when P0111 is logged.
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1
Faulty IAT sensor (internal thermistor failure)
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2
Corroded or damaged IAT sensor connector or wiring
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3
IAT sensor contaminated with oil vapour from CCV/PCV system
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4
Failed MAF sensor with integrated IAT element
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5
Intermittent open or short circuit in the signal wire
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6
Unstable 5 V reference voltage from PCM
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7
Air leaks between the MAF and throttle body (unmetered air)
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8
PCM fault or corrupted calibration data
Symptoms drivers notice
How to diagnose P0111
A typical diagnostic flow when this code is present.
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1
Connect a scan tool and check live IAT sensor data; compare the reading to actual ambient temperature — a large discrepancy confirms a faulty signal
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2
Inspect the IAT sensor connector for corrosion, bent pins, or moisture; clean contacts with electrical contact cleaner and recheck
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3
Measure the 5 V reference voltage at the sensor connector with KOEO; it should be 4.8–5.2 V
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4
With the sensor disconnected, measure resistance across the IAT terminals and compare against the manufacturer temperature-resistance table; extreme or out-of-spec values indicate a failed thermistor
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5
Check for continuity and insulation resistance on the signal and ground wires between the sensor and PCM; any short or open indicates wiring damage
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6
Inspect the intake tract for oil contamination from the CCV/PCV system; clean or replace the separator and sensor if fouled
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7
If the IAT is integrated into the MAF sensor, also test MAF output voltage and frequency against specification
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8
Clear the code and run a complete warm-up drive cycle to verify the fix
Vehicles where we've handled P0111
Platforms in our catalogue with confirmed P0111 coverage.
Related powertrain codes
- P0068 — MAP/MAF - Throttle Position Correlation
- P006A — MAP - Mass or Volume Air Flow Correlation Bank 1
- P00B8 — MAP - Mass or Volume Air Flow Correlation Bank 2
- P00BC — Mass or Volume Air Flow A Circuit Range/Performance - Air Flow Too Low
- P00BD — Mass or Volume Air Flow A Circuit Range/Performance - Air Flow Too High
- P00BE — Mass or Volume Air Flow B Circuit Range/Performance - Air Flow Too Low
Frequently asked questions
Can P0111 cause damage if ignored?
On naturally aspirated engines it is unlikely to cause immediate damage, but fuelling inaccuracy and degraded cold-start enrichment can increase wear and emissions. On turbocharged engines, incorrect IAT data can cause incorrect boost targets, so prompt repair is more important.
Is the IAT sensor the same as the MAF sensor?
Not always. On many modern vehicles the IAT thermistor is integrated into the MAF sensor housing. On older designs it is a separate two-wire sensor mounted in the air intake pipe. Check your vehicle's service data to determine which configuration applies.
Why does P0111 appear only when the engine is warm?
The PCM often cross-checks the IAT reading against the ECT sensor and an ambient temperature model after the engine has warmed up. A sensor that reads plausibly cold but fails to track rising intake temperatures correctly will only be flagged once this comparison is active — typically after a full warm-up cycle.
Can a dirty air filter cause P0111?
Indirectly, a severely restricted air filter can reduce airflow enough to cause abnormal temperature stratification in the intake, but this is rarely the primary cause of P0111. It is worth checking as part of a general inspection, but wiring and sensor condition are higher-priority checks.
Will P0111 affect a modified or remapped ECU differently?
Yes. After an ECU remap the fuel and boost maps are typically calibrated with accurate IAT correction tables. A faulty IAT reading on a remapped engine can cause the ECU to apply incorrect fuelling or boost corrections, potentially worsening performance or safety margins compared to a stock calibration.
Disabling P0111 in software
RaceTune can permanently disable P0111 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
ECUs with a P0111 disable in our catalogue
Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.
- Bosch EDC17C50 verified 1 software version
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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