P27FA
Intake Air Temperature Sensor 2 Circuit Range/Performance (Bank 1)P27FA is a generic OBD-II powertrain diagnostic trouble code: Intake Air Temperature Sensor 2 Circuit Range/Performance (Bank 1). It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P27FA means
P27FA is set when the PCM determines that the signal from intake air temperature (IAT) sensor 2 on bank 1 is present but does not correlate correctly with other sensor inputs or expected operating conditions. Unlike circuit-high or circuit-low codes, a range/performance fault means the sensor is electrically functional but its readings are implausible given the engine operating context.
IAT sensor 2 is typically located downstream of the intercooler or in the intake manifold, measuring charge air temperature after cooling. The PCM uses this data to fine-tune fuel delivery, ignition timing, and boost pressure. If the sensor reads a temperature inconsistent with coolant temperature at cold start, ambient conditions, or the known intercooler efficiency, the PCM flags the discrepancy.
Common causes include a sensor that has shifted its calibration over time, a partially contaminated sensor element with oil or moisture, or intermittent wiring issues that produce plausible but incorrect voltage levels. Since this is a performance code, static bench testing may not reveal the fault; monitoring sensor response during warm-up and under load is often necessary to isolate the root cause.
Common causes
Most-frequently reported root causes when P27FA is logged.
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1
Degraded IAT sensor 2 element with shifted calibration producing plausible but inaccurate temperature readings.
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2
Oil or moisture contamination on the sensor element affecting its thermal response.
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3
Intermittent wiring fault causing the signal to read incorrectly under vibration or thermal cycling.
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4
Corroded sensor connector creating a variable resistance that skews the temperature reading.
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5
IAT sensor 2 located in a position with poor airflow, giving stagnant rather than charge-air readings.
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6
Coolant leak into the intake tract near the sensor affecting its readings.
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7
Failed intercooler reducing charge air cooling and causing unexpectedly high IAT2 readings.
Symptoms drivers notice
How to diagnose P27FA
A typical diagnostic flow when this code is present.
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1
Read and record all DTCs and freeze-frame data; note ambient temperature and engine coolant temperature at the time of the fault.
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2
Compare IAT sensor 2 live data to ambient temperature on a cold start; they should be within a few degrees of each other and of IAT sensor 1.
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3
Inspect the sensor and connector for oil contamination, moisture, or corrosion.
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4
Check wiring from sensor to PCM for intermittent opens or high-resistance connections.
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5
Warm the engine to operating temperature and compare IAT sensor 2 readings to expected intercooler outlet temperatures for the conditions.
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6
Replace IAT sensor 2 if its readings deviate significantly from IAT sensor 1 or from expected values after the harness is confirmed good.
Vehicles where we've handled P27FA
Platforms in our catalogue with confirmed P27FA coverage.
Related powertrain codes
- P2700 — Friction Element A Apply Time Range/Performance
- P2701 — Friction Element B Apply Time Range/Performance
- P2703 — Friction Element D Apply Time Range/Performance
- P2704 — Friction ElementEApply Time Range/Performance
- P2705 — Friction ElementFApply Time Range/Performance
- P2706 — Solenoid F Malfunction
Frequently asked questions
What is the difference between IAT sensor 1 and IAT sensor 2?
IAT sensor 1 is typically upstream of the intercooler measuring ambient or pre-compressor air temperature, while IAT sensor 2 measures post-intercooler charge air temperature closer to the intake manifold.
Can a dirty sensor cause P27FA?
Yes. Oil or carbon contamination on the sensor element can insulate it thermally, causing it to read sluggishly or inaccurately and triggering a performance code.
Is P27FA a serious fault?
It is typically not immediately critical, but the PCM may use conservative timing and fuelling corrections that reduce performance and fuel economy until the fault is resolved.
Will P27FA cause a failed emissions test?
Yes. An active MIL will cause an automatic emissions test failure in most inspection programs, regardless of whether the fault affects tailpipe emissions directly.
Disabling P27FA in software
RaceTune can permanently disable P27FA — 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 P27FA 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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