What does P0101 mass airflow sensor range or performance mean?
Short answer: P0101 means the airflow reading does not make sense compared with what the computer expects from engine speed, throttle and manifold pressure, often from a dirty sensor, an air leak or a restricted intake.
The computer predicts how much air the engine should be pulling based on rpm, throttle position and manifold pressure or barometric pressure. When the mass airflow sensor reading falls outside that expectation, it sets a range or performance code rather than a simple circuit code.
Inspect the intake first: a dirty or oiled air filter, a collapsed duct, or a cracked boot after the sensor all upset the reading. Unmetered air leaking in after the sensor makes it read low compared with what the engine actually breathes. Contamination on the sensing element from dirt or over-oiled filters is common too.
On a scan tool, compare grams per second at idle and at a steady 2500 rpm with known-good values for that engine size, and watch how the reading responds to a snap throttle. Use only cleaner made for airflow sensors if you clean it, and check wiring and ground before replacing it.
Tools used for this job
General guidance only. Follow the vehicle and tool manufacturer's procedures, and confirm vehicle coverage on the tool maker's list before buying.