P0102 serious

Mass Air Flow Circuit Low Input

What does P0102 mean?

The P0102 code means the vehicle's onboard diagnostic system has detected: Mass Air Flow Circuit Low Input. This is a serious severity code.

Common Symptoms

  • Check Engine Light on
  • Poor acceleration
  • Engine runs lean
  • Rough idle
  • Fuel economy drops

Probable Causes (Ranked by Likelihood)

  • Faulty MAF sensor producing low voltage Very High
  • Open circuit or poor ground in MAF wiring High
  • Contaminated MAF sensor element Moderate
  • Air filter severely clogged Moderate
  • Wiring short to ground Low

Step-by-Step Diagnostic Procedure

  1. Check MAF signal voltage at idle (typically 0.5-1.5V for analog sensors). Below 0.3V indicates a short.

  2. Inspect wiring from MAF sensor to PCM for damage, corrosion, or breaks.

  3. Verify the MAF sensor has proper 5V reference and ground.

  4. Clean the MAF sensor and retest.

  5. Temporarily substitute a known-good MAF sensor to confirm diagnosis.

Frequently Asked Questions

Will P0102 cause my car to run rich or lean?

A low MAF signal tells the ECU less air is entering than actual. The ECU reduces fuel delivery, resulting in a lean condition. This can trigger P0171 or P0174 fuel trim codes as well.

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