P0100 fault code: Mass or Volume Air Flow Circuit

P0100 means “Mass or Volume Air Flow Circuit” — a fuel and air metering fault in the powertrain.

Can I DIY?

Professional-only boundary. Confirm P0100 on a scanner; cleaning or replacing the air-flow meter is not published here.

Do not DIYReviewed page boundary
ToolsSpecialist equipment

This is the conservative boundary from the reviewed code record. This page has no frozen site-wide safety grade, so it does not publish a repair route.

What to tell the garage about P0100

Do not drive. The mass or volume air-flow circuit as a whole has failed a check, so the computer may not know how much air is entering the engine.

Take these reviewed, code-specific details with you. They help the garage confirm the fault without turning this page into a repair procedure.

  • Mass or Volume Air Flow Circuit: Registration number
  • Mass or Volume Air Flow Circuit: Exact code P0100 and any P0101–P0104 or fuel-trim codes
  • Mass or Volume Air Flow Circuit: Whether the engine hunts, hesitates, or feels down on power
  • Mass or Volume Air Flow Circuit: Whether the air-filter box looked obviously unlatched (look only, engine cold)
P01xxFuel and air metering
MOT fail riskif the warning light stays on

What does P0100 mean?

P0100 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P01xx block, which covers fuel and air metering. The stored description is “Mass or Volume Air Flow Circuit”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0100 fail an MOT?

An illuminated engine management light is a Major defect at MOT until repaired and the lamp stays off. P0100 is a general air-flow circuit fault, not an MOT exhaust-emissions figure.

Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.

Related guides

Car diagnostic test cost: compare the scopeUK booking marketplaces currently publish diagnostic averages of about £52–£65. Engine management light on: steady or flashing?A steady engine management light means the computer has stored a fault. Drive with caution and get the code read. A flashing light is different — stop when it is safe. Car loses power when accelerating: safe next stepsReduced power is a symptom, not a parts diagnosis; leave fast traffic and preserve warning and code evidence.
P0101Mass or Volume Air Flow Circuit Range/Performance P0102Mass or Volume Air Flow Circuit Low Input P0103Mass or Volume Air Flow Circuit High Input P0104Mass or Volume Air Flow Circuit Intermittent P0105Manifold Absolute Pressure/Barometric Pressure Circuit P0106Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance P0107Manifold Absolute Pressure/Barometric Pressure Circuit Low Input P0108Manifold Absolute Pressure/Barometric Pressure Circuit High Input

P0100 — quick answers

Is it safe to drive with P0100?

Do not drive. We have no verified driving guidance for P0100 — treat as do not drive until checked. Neighbour MAF codes are graded; this general circuit code is not, so it is not treated as a driveway clean.

Will P0100 fail my MOT?

An illuminated engine management light is a Major defect at MOT until repaired and the lamp stays off. P0100 is a general air-flow circuit fault, not an MOT exhaust-emissions figure.

Fault-code identifiers are standard diagnostic facts. Their explanations and diagnostic guidance on this site are original editorial summaries, not reproduced SAE wording. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.