OBD-II CODE / Fuel & air
P0101 · Mass or volume airflow signal out of expected range
The measured airflow fell outside the range the computer expected for those operating conditions.
Part of the Fuel trim system guide.
What range or performance tells you
The module can see a signal that disagrees with its airflow estimate. Intake restrictions, leaks, sensor or connector problems and vehicle-specific calibration issues lead to different tests.
Compare the evidence
Use the freeze frame to find the speed and load where the issue appeared. Inspect the intake duct and connectors with the engine off. A technician can compare the airflow reading with vehicle-specific reference data.
A vehicle-specific example
Volkswagen tech tip 21-20-01TT tells technicians to inspect a charge-air connection on listed models when P0101 is present. A loose connection can affect measured airflow without an internal sensor failure.