Code
P1111
SUBARU
P — Powertrain
Atmospheric Pressure Sensor High Input
AI status
Completed
Completed
100%
Causes
- Faulty atmospheric/barometric (BARO) pressure sensor
- Short in sensor signal wire to battery/ignition voltage
- Poor or corroded ground or connector at sensor
- Damaged or chafed wiring harness (intermittent short/high resistance)
- Incorrect replacement sensor or connector mismatch
- ECM input circuit fault (less common)
Symptoms
- Malfunction Indicator Lamp (MIL)/Check Engine light illuminated
- Poor idle quality or rough running
- Hard starting or extended cranking
- Reduced engine performance, hesitation or stumbling
- Erratic fuel trim readings and increased emissions
- Possible issues with boost/charge control on turbo models
What to check
- Read and record freeze-frame and live data with a scan tool
- Verify code P1111 is current vs stored; clear code and see if it returns
- Visually inspect sensor, connector and wiring for damage, corrosion, or loose pins
- Backprobe sensor connector and measure signal voltage, reference voltage and ground at key‑on and engine running
- Check continuity and for shorts between signal wire and battery (+) and signal wire and ground
- Compare live BARO sensor reading to known ambient pressure (barometric) or MAP at key‑on
Signal parameters
- Typical BARO/MAP sensor reference: 5V reference (commonly 5V)
- Expected sensor signal range (typical): ~0.5–4.5 V depending on design (atmospheric pressure near top end at sea level)
- At key‑on engine off the BARO signal should approximate ambient pressure value (near expected upper range at sea level)
- High input fault: signal exceeds normal maximum or is pegged near Vref or battery voltage
Diagnostic algorithm
- Connect a scan tool, verify P1111 and note freeze‑frame data; unplugging sensor and checking default/backup values may help diagnosis.
- With ignition ON (engine OFF) monitor BARO signal voltage and compare to expected ambient reading; record voltage.
- Measure sensor reference voltage (should be stable ~5V or specified value) and chassis/ECM ground quality at sensor connector.
- Unplug the sensor: if the ECM reports a different default value or the code behavior changes, suspect sensor or wiring. If signal remains high with sensor disconnected, suspect ECM.
- Inspect wiring harness from sensor to ECM for damage, pin corrosion, rodent damage or connector issues. Check continuity and resistance of signal wire; check for short to battery (+) with ohmmeter and power diode test.
- Repair or replace damaged wiring or connectors. If wiring and connectors OK, replace BARO sensor with OEM or specified unit.
- After repair, clear codes and test-drive while monitoring live data to ensure correct BARO readings and no return of P1111.
- If problem persists after sensor and wiring replacement, test or replace ECM per manufacturer service procedures.
Likely causes
- Failed BARO sensor
- Shorted signal wire to +12V or sensor Vref
- Corroded connector or poor ground at sensor
- Wiring harness damage between sensor and ECM
- ECM internal fault (verify after wiring/sensor checks)
Fault status
Status
Atmospheric Pressure Sensor High Input — sensor circuit voltage above expected range (signal higher than allowed), causing incorrect barometric input to ECM.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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