P0021 fault code: 'A' Camshaft Position - Timing Over-Advanced or System Performance

P0021 means “'A' Camshaft Position - Timing Over-Advanced or System Performance” — a fuel and air metering fault in the powertrain.

Can I DIY?

Professional-only boundary. Do not pour additives to 'free' a VVT phaser for P0021.

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 P0021

Do not drive until checked. Camshaft A on the P002x bank is earlier than commanded, or the VVT system failed its performance test. Over-advanced cam A is a workshop angle diagnosis.

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

  • 'A' Camshaft Position - Timing Over-Advanced or System Performance: Registration number
  • 'A' Camshaft Position - Timing Over-Advanced or System Performance: Exact code P0021 and any companion codes from the same scan
  • 'A' Camshaft Position - Timing Over-Advanced or System Performance: Whether the engine management light is steady or flashing
  • 'A' Camshaft Position - Timing Over-Advanced or System Performance: Cold-start noise and last oil specification used
P00xxFuel and air metering
MOT fail riskif the warning light stays on

What does P0021 mean?

P0021 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P00xx block, which covers fuel and air metering. The stored description is “'A' Camshaft Position - Timing Over-Advanced or System Performance”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0021 fail an MOT?

DVSA MOT inspection fails a lit engine management light as Major. P0021 is over-advanced or poor-performance cam A on the P002x bank, not the over-retarded P0022 flag.

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.
P0001Fuel Volume Regulator Control Circuit/Open P0002Fuel Volume Regulator Control Circuit Range/Performance P0003Fuel Volume Regulator Control Circuit Low P0004Fuel Volume Regulator Control Circuit High P0005Fuel Shutoff Valve 'A' Control Circuit/Open P0006Fuel Shutoff Valve 'A' Control Circuit Low P0007Fuel Shutoff Valve 'A' Control Circuit High P0008Engine Position System Performance

P0021 — quick answers

Is it safe to drive with P0021?

Do not drive until checked. We have no verified driving guidance for P0021. Treat as do not drive until checked. Over-advanced cam A is not a DIY oil-flush fix.

Will P0021 fail my MOT?

DVSA MOT inspection fails a lit engine management light as Major. P0021 is over-advanced or poor-performance cam A on the P002x bank, not the over-retarded P0022 flag.

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.