What it means
The Mass or Volume Air Flow B circuit reading is above the expected range or does not perform as expected.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Mass air flow sensor B measures airflow through a second monitored air path or sensor arrangement, where fitted. The control module checks sensor B's signal against expected airflow for engine operation. P00BF sets when sensor B reports airflow that is too high or otherwise fails the expected range or performance check.
Common causes
Most likely first.
- MAF B reading drifted high
- Sensor element aged beyond calibration window
- Sensor mounting loose - signal damping
Symptoms
- Check engine light on
- Rough idle or hesitation
- Reduced power
- Fuel economy may worsen
How to diagnose it
- Read freeze-frame data and compare sensor B's airflow reading with engine speed, load, and any corresponding sensor A reading.
- Identify sensor B's location from vehicle service information and inspect its air path and mounting for looseness, leaks, or disturbed airflow.
- Check sensor B's element for contamination and inspect its connector and wiring for damage or poor contact.
- Observe sensor B in live data as engine speed and load change, checking whether it responds smoothly and plausibly relative to sensor A.
- If the reading remains high, test sensor B's signal and circuit against the manufacturer's specification before replacing it.
Common fixes
- Secure sensor B's loose mounting or correct air-path fitment problems at its location.
- Repair leaks or loose connections in the air path monitored by sensor B.
- Clean the sensor B element only with a method and cleaner approved for that sensor.
- Repair sensor B wiring or connector faults, or replace sensor B if testing confirms high or drifting output.
Can I keep driving?
If the vehicle remains smooth and responsive, drive gently and watch for hesitation or power loss. Avoid hard acceleration if symptoms occur, since an overreported airflow signal can cause incorrect fueling and emissions.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.