P0321 fault code: Ignition/Distributor Engine Speed Input Circuit Range/Performance

P0321 means “Ignition/Distributor Engine Speed Input Circuit Range/Performance” — an ignition system and misfire fault in the powertrain.

Can I DIY?

Professional-only boundary. No unique checks for P0321. Confirm the code and book a garage. Do not 'tune' a distributor from this page.

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 P0321

Do not drive. The engine-speed input from the ignition or distributor circuit is out of range or performing poorly. Unexpected stalling is a reason to stop; workshop diagnosis is required.

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

  • Ignition/Distributor Engine Speed Input Circuit Range/Performance: Registration number
  • Ignition/Distributor Engine Speed Input Circuit Range/Performance: Exact code P0321 and any P0320, P0322, or position-sensor codes
  • Ignition/Distributor Engine Speed Input Circuit Range/Performance: Whether rpm on a scan tool looks frozen, jumpy, or missing
  • Ignition/Distributor Engine Speed Input Circuit Range/Performance: Whether the engine stalls or will not rev cleanly
P03xxIgnition system and misfire
MOT fail riskif the warning light stays on

What does P0321 mean?

P0321 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P03xx block, which covers ignition system and misfire. The stored description is “Ignition/Distributor Engine Speed Input Circuit Range/Performance”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0321 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. Flashing engine management light and juddering: stop and recoverNo — do not continue the journey. A flashing engine management light with the car juddering is a stop-driving situation: ease off only enough to reach the nearest place of relat…
P0300Random/Multiple Cylinder Misfire Detected P0301Cylinder 1 Misfire Detected P0302Cylinder 2 Misfire Detected P0303Cylinder 3 Misfire Detected P0304Cylinder 4 Misfire Detected P0305Cylinder 5 Misfire Detected P0306Cylinder 6 Misfire Detected P0307Cylinder 7 Misfire Detected

P0321 — quick answers

Is it safe to drive with P0321?

Do not drive. Driveability guidance is not available for this code — treat as do not drive until checked.

Will P0321 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.