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Home / DTC / P0103 — AFS high input

P0103 — AFS high input

Detailed page for trouble code P0103.

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Code

P0103

MITSUBISHI P — Powertrain

AFS high input

Brand: MITSUBISHI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to battery (signal wire shorted to +12V)
  • Damaged or contaminated air flow sensor (hot-wire or vane type)
  • Corroded, bent or pushed-back connector pins
  • Faulty ground or poor reference voltage from PCM
  • Intermittent/shorted wiring harness (chafing, crushed, rodent damage)
  • Aftermarket intake/MAF modifications or filter oil contamination

Symptoms

  • MIL/Check Engine Light illuminated
  • Engine runs rich (black exhaust smoke, poor fuel economy)
  • Rough idle, hesitation or stumbling on acceleration
  • Stalling at idle or low speed
  • Poor drivability under load

What to check

  • Read and record stored DTCs and freeze frame data with a scan tool
  • Inspect air intake, MAF/AFS connector and wiring for damage, corrosion, loose pins or melted insulation
  • Visually inspect air filter and intake for oil or heavy contamination on the sensor element
  • With key ON (engine OFF) backprobe the sensor connector: verify reference voltage (typically 5 V or manufacturer specified) and good ground
  • Measure signal voltage at sensor with engine running and compare to live data on scan tool
  • Check continuity between signal wire and battery positive (to detect a short to +12V) and between signal and ground for shorts

Signal parameters

  • Typical reference voltage: ~5.0 V (verify factory specification)
  • Signal range: ~0.0–5.0 V (idle commonly 0.5–1.5 V; high airflow near 4.0–5.0 V) — values vary by sensor type
  • Ground: 0 V reference
  • When P0103 is set the ECU is seeing signal voltage above its high threshold (sensor-specific)

Diagnostic algorithm

  1. Connect a scan tool, read DTCs and freeze frame; note engine load, rpm and sensor voltage at fault time.
  2. Perform a visual inspection of the AFS/MAF wiring harness, connector and sensor for damage, contamination or oil on the sensor element.
  3. With ignition ON (engine OFF) backprobe connector: verify reference voltage and ground presence. Record values.
  4. Measure signal voltage with engine idling and at increased rpm while watching live data. If voltage is abnormally high at key ON or unplugging sensor changes behavior, suspect wiring short to +12V.
  5. Check continuity from signal pin to battery positive to detect a short to power; repair any shorted wiring.
  6. Clean contaminated sensor only if manufacturer permits; if element remains abnormal, replace the AFS/MAF sensor.
  7. After wiring repair or sensor replacement clear codes and road test. Re-scan to confirm code does not return.
  8. If fault persists with good sensor and repaired wiring, suspect PCM fault and refer to dealer-level diagnostics or PCM replacement as last step.

Likely causes

  • Short in signal wire to +12V at harness/connector
  • Contaminated hot-wire element from oil or dirt causing erratic/high output
  • Damaged sensor element internally producing high voltage
  • Corroded connector pin raising measured voltage
  • Bad PCM reference or damaged ground circuit

Fault status

⚠️ Status
P0103 — AFS (air flow sensor) high input detected: sensor signal voltage above expected threshold. Possible short to battery, damaged/contaminated sensor, wiring/connector fault, or less commonly ECU issue.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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