Powertrain fault code
P0101: Mass or Volume Air Flow Sensor "A" Circuit Range/Performance
Fix soon
Usually safe to drive gently to a workshop, but fuel use and running can suffer. Have it checked soon.
What P0101 means
The engine computer is getting a reading from the mass air flow sensor that is missing, out of range or doesn't make sense. The mass air flow sensor measures how much air enters the engine.
Common causes
- Dirty or contaminated MAF sensor
- Air leak between the MAF and the throttle body
- Blocked or badly fitted air filter
- Damaged wiring or connector
What to check first
- Scan the car to confirm the code and see if others are stored with it.
- Check the sensor plug and wiring for corrosion, damage or a loose connection.
- Compare the live sensor reading with a known-good value before replacing the part.
P0101 on popular makes
P0101 on a Nissan
- A dirty or failing mass air flow (MAF) sensor is the most commonly reported cause on Nissans.
- Oiled aftermarket air filters can coat the MAF sensor wire; clean it with MAF cleaner only and never touch the wire.
- After cleaning or replacing parts, many Nissans need an "idle air volume learn" (a workshop scan tool can run it) so the idle settles.
P0101 on a Toyota
- Check that the air filter box is clipped shut and the intake hose between the MAF and throttle body has no cracks.
- Cleaning the MAF sensor with MAF cleaner often fixes it; replace it only if live readings stay wrong.
Read your car's codes yourself, free
Plug a cheap ELM327 OBD-II adapter into the port under the dashboard and open the scan tool: Chrome or Edge on a computer with a USB adapter, or Chrome on Android with a Bluetooth LE adapter. It reads and clears codes and shows emissions readiness. It does not work on iPhone.
Open the free scan toolRelated codes
General guidance only, not a diagnosis. A qualified mechanic should confirm the cause before you replace parts.