P0129 fault code: Barometric Pressure Too Low

P0129 means “Barometric Pressure Too Low” — a fuel and air metering fault in the powertrain.

Can I DIY?

Professional-only boundary. Confirm the stored code only; barometric-pressure diagnosis 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 P0129

Do not drive. Outside-air (barometric) pressure is arriving below the band the engine computer expects. That figure is used to meter incoming air against fuel. It is a pressure-plausibility flag, not a burst-hose confirmation.

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

  • Barometric Pressure Too Low: Registration number
  • Barometric Pressure Too Low: Exact code P0129 and any companion codes
  • Barometric Pressure Too Low: Whether the engine management light is steady or flashing
  • Barometric Pressure Too Low: Whether the car felt gutless, hunted, or hard to start in thin-air or weather changes
P01xxFuel and air metering
MOT fail riskif the warning light stays on

What does P0129 mean?

P0129 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 “Barometric Pressure Too Low”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0129 fail an MOT?

An illuminated engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off.

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

P0129 — quick answers

Is it safe to drive with P0129?

Do not drive. We have no verified driving guidance for a low barometric-pressure flag, so we do not invent a milder rating. Park the car and have a garage confirm the pressure reading before treating it as normal to drive.

Will P0129 fail my MOT?

An illuminated engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off.

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.