P0109 fault code: Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

P0109 means “Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent” — a fuel and air metering fault in the powertrain.

Can I DIY?

Professional-only boundary. Log P0109; reproducing an intermittent MAP glitch on a live engine is garage work.

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 P0109

Do not drive. Manifold or barometric pressure is intermittent, so load calculations can jump between a plausible figure and a nonsense one.

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

  • Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent: Registration number
  • Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent: Exact code P0109 and how often it returns
  • Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent: Whether it sets on bumps, when hot, or in the wet
  • Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent: Companion P0105–P0108 or fuel-trim codes
P01xxFuel and air metering
MOT fail riskif the warning light stays on

What does P0109 mean?

P0109 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 “Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0109 fail an MOT?

An illuminated engine management light is a Major defect at MOT until repaired and the lamp stays off. P0109 is intermittent; absence of the lamp on the day of test does not clear the stored fault for the computer.

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.
P0100Mass or Volume Air Flow Circuit 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

P0109 — quick answers

Is it safe to drive with P0109?

Do not drive. We have no verified driving guidance for P0109 — treat as do not drive until checked. An intermittent MAP circuit can glitch in traffic; it is not a 'clear and ignore' code.

Will P0109 fail my MOT?

An illuminated engine management light is a Major defect at MOT until repaired and the lamp stays off. P0109 is intermittent; absence of the lamp on the day of test does not clear the stored fault for the computer.

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.