P0101Mass or Volume Air Flow Sensor A Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- The mass air flow sensor (MAF) sits between the air filter and the throttle or compressor and measures how much air the engine draws in; fuel quantity, load and ignition are calculated from it. Most are hot-film or hot-wire sensors that output either a voltage or, on GM, Saab and newer Ford systems, a frequency. P0101 is a plausibility fault: the signal is electrically fine but does not match the engine's state. GM petrol engines model the expected air flow from manifold pressure, throttle, speed and boost and blame the MAF if it is off by more than 20 g/s; GM diesels check the measured-to-estimated ratio (0.8–1.2) with EGR closed; Bosch ME9 compares it with the throttle angle. Common causes are air leaks after the sensor, a soiled element (oiled sport filters) or a disconnected crankcase vent; GM also documents a bad crimp in the fuse box. Ford uses P0068 instead. Two trips are needed.
- What you may notice
- Check engine light on, often without driveability problems
- Hesitation, flat spot, poor throttle response
- Rough idle or stalling
- Higher consumption, often with lean codes P0171/P0174
- Likely causes
- LikelyAir leak between sensor and engine (cracked or loose intake duct, boost leak)
- LikelyContaminated sensing element (oil from oiled sport filter, dust)
- PossibleLeaking or disconnected crankcase ventilation
- PossibleClogged or wrongly fitted air filter, modified intake
- PossibleAged sensor or poor contact in the wiring
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €10 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.