P0170 fault code: Fuel Trim

P0170 means “Fuel Trim” — a fuel and air metering fault in the powertrain.

Can I DIY?

Professional-only boundary. Observe the lamp only; fuel-trim diagnosis for P0170 is garage work.

Do not DIYReviewed page boundary

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 P0170

Do not drive. Long- or short-term fuel trim on this monitor has left the band the computer will accept. The title does not say rich or lean — only that adaptation has gone out of range on this trim channel.

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

  • Fuel Trim: Number plate
  • Fuel Trim: Exact code P0170 and any P0171/P0174 companion stores
  • Fuel Trim: Whether the engine hunts, smells of fuel, or lacks power
P01xxFuel and air metering
MOT fail riskif the warning light stays on

What does P0170 mean?

P0170 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 “Fuel Trim”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0170 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

P0170 — quick answers

Is it safe to drive with P0170?

Do not drive. We have no verified driving guidance for P0170. Treat as do not drive until a garage reads freeze-frame trim. Do not copy the P0171 lean-bank driving advice onto this unspecified trim malfunction.

Will P0170 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.