OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P0101

Mass or Volume Air Flow Circuit Range/Performance

The mass air flow (MAF) sensor signal is outside the expected range or does not track engine load plausibly. The ECU compares MAF readings against load calculated from RPM, throttle position and intake pressure; persistent disagreement triggers this code.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number1 / 01

Possible causes

  • MAF sensor contaminated (oil, dust) high
  • Unmetered air leak after MAF medium
  • Air filter heavily clogged medium
  • Wiring/connector fault to MAF low

Inspection / repair

  • Difficulty: easy
  • DIY: possible
  • Estimated cost: 50–250 €
  • Estimated time: 0.3–1.5 h
  • Component: mass air flow sensor
  • Component: air filter
  • Component: intake duct
  • Component: intake manifold
  • MIL / check engine light
  • emissions-relevant
  • drive cycle required

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication