P0101 fault code: mass air flow sensor reading problem
Plain-language definition
Mass or Volume Air Flow Sensor A Circuit Range/Performance
What does it mean?
The mass air flow sensor (MAF) sits between the air filter and the engine and measures how much air goes into the engine. The engine computer uses this to calculate how much fuel to inject; on diesel engines it also relies on this measurement when adjusting the EGR system.
P0101 is stored when the sensor's signal is electrically within limits but the amount of air it measures doesn't match data such as engine speed, throttle position or intake pressure. In other words, the sensor is sending a signal, but the engine computer doesn't trust the value. The problem isn't always the sensor: an air leak after the sensor or a clogged air filter can also skew the reading.
You may notice less power, a fluctuating idle, the car misfiring when accelerating, or higher fuel consumption. On diesel cars there may be black smoke from the exhaust; sometimes there's no symptom other than the check engine light.
How serious is it?
It's a Warning-level code. Because the engine computer may set the mixture using wrong air data, fuel consumption and the way the car drives can be affected as long as the problem continues; on diesel cars, the extra soot can also fill the diesel particulate filter (DPF) faster.
Severity is a guide; if the warning light is flashing or you notice symptoms while driving, have the car checked at a workshop.
Common general causes
- The air flow sensor's measuring element contaminated with dust or oil fumes
- An air leak in the intake after the sensor (a cracked hose, a loose clamp)
- A clogged or incorrectly fitted air filter
- The sensor wearing out with age, or failing
- On diesel cars, problems that change the air flow, such as the EGR valve staying open
- A poor contact in the sensor connector or wiring
The list shows general causes; a workshop finds the actual cause on your car with a check.
Related codes
How does it appear in the 2dakika report?
Mass or Volume Air Flow Sensor A Circuit Range/Performance
If the code is read as a confirmed (stored) fault, the report shows it with the "Warning" severity; in pending or past records, codes that don't request the warning light and aren't critical appear as "Info". If the engine computer stored them, the conditions when the fault was recorded (engine temperature, rpm, speed) are shown too.
Read this code with the OBD-X1, and clear it from the app after the repair.
Clearing the code doesn't fix the fault; if the problem persists, the code comes back.