Engine codes
P0101: mass air flow sensor range or performance
The mass air flow sensor tells the engine computer how much air is coming in, and fuel is metered from that number. P0101 is set when the reading is plausible electrically but does not fit what throttle, speed and manifold pressure predict.
P0101: can I drive, and what will the labor cost?
Estimated labor, clean the maf sensor and replace the air filter
$22 to $44
| Labor time (estimate) | 0.2 to 0.4 h |
| Rate used | $110/h |
| Technician wage, United States (average) | $27.13/h |
| Moderate: fix within weeks Drivable, but expect hesitation or poor mileage; fix within a few weeks so the fuel mixture does not stay off. | |
Labor only: parts and the diagnostic fee are not included. Hours are our estimate for a typical car; book times vary by model. Wage: BLS, May 2025.
P0101 is the generic OBD-II code for "mass or volume air flow sensor A circuit range or performance". Unlike the circuit codes P0102 and P0103, which mean a signal that is too low or too high to be real, P0101 means the signal is in range but wrong for the conditions: the computer has compared it with a value it calculates from engine speed, throttle angle and, on many cars, a manifold pressure sensor, and found too wide a gap. The usual reasons are cheap. A film of dirt or oil on the hot-wire element makes the sensor under-read, and a split rubber boot between the sensor and the throttle lets in air that is never measured. A blocked or over-oiled air filter comes next, and a failed sensor last. It is drivable, with hesitation and poor mileage, and often travels with lean codes P0171 and P0174.
Read your fuel trims (from a scanner's live data)
Total trim at idle / 2,500 rpm
+20% / +6%
| Reading: Lean at idle that improves with engine speed: the pattern of a vacuum leak. |
Positive trims mean the computer is adding fuel. This idle-versus-speed comparison is a common shop test, not a rule: confirm with a smoke test or a fuel pressure gauge. Negative values can be typed with a minus sign.
Codes, rules and labor data checked by Radif Partners · Editorial policy · Method and sources
P0101 at a glance
| Code | P0101 |
| Standard description | Mass or Volume Air Flow Sensor "A" Circuit Range/Performance |
| System | Air metering and throttle |
| Severity | Moderate: fix within weeks |
| Common symptoms | hesitation on acceleration, rough idle, stalling, poor fuel economy |
Why cleaning comes before replacing
The sensing element is a heated wire or film in the air stream. Dust that passes a worn filter, oil from an over-oiled reusable filter and blow-by vapors coat it over the years, and a coated element cools more slowly, so it reports less air than is really flowing. A spray made specifically for air flow sensors, used with the sensor removed and the connector unplugged, is the usual first step. Carburetor or brake cleaner can damage the element and should not be used.
The leak after the sensor
Every gram of air that enters after the sensor is invisible to it. A cracked intake boot, a loose clamp, a disconnected breather hose or an oil filler cap left loose all create the same effect as a dirty sensor. A smoke test of the intake finds most of these in minutes. Long-term fuel trims that are high at idle and closer to normal at higher speed point to a leak; trims that are high everywhere point more to the sensor or to fuel delivery. The fuel trim reader on this page helps you read those values from a scanner.
If you replace the sensor, a quality part matters: inexpensive replacements are a frequent cause of P0101 returning. Compare with P0171 if a lean code is also stored.
Likely causes of P0101, in order
| Cause | How often |
|---|---|
| Dirty or contaminated MAF sensing element | most frequent |
| Unmetered air: cracked intake boot or loose clamp after the sensor | most frequent |
| Clogged or over-oiled air filter | frequent |
| Failed MAF sensor | frequent |
| Wiring or connector fault | less frequent |
P0101 repairs and labor time
| Repair | Labor (estimate) | At $110/h |
|---|---|---|
| Clean the MAF sensor and replace the air filter | 0.2 to 0.4 h | $22 to $44 |
| Replace the intake air duct or boot | 0.3 to 1 h | $33 to $110 |
| Replace the MAF sensor | 0.3 to 0.6 h | $33 to $66 |