P0300 fault code: Random/Multiple Cylinder Misfire Detected

Last updated · OBDCode UK editorial

Self-drawn engine management light for P0300 random misfire, steady or flashing
Decorative labelled telltale: a steady or flashing engine management light, the lamp P0300 usually sets. Normally amber. A flashing lamp is more serious than a steady one. This drawing is not manufacturer artwork and does not name any other colour.
Can I drive with P0300? — Limited driving only

Limit driving with a steady light and mild roughness. If the engine management light is flashing and the car judders, stop when safe and arrange recovery — continuing can destroy the catalyst.

P0300 means “Random/Multiple Cylinder Misfire Detected” — an ignition system and misfire fault in the powertrain. Limited driving only. Combustion is failing on more than one cylinder, or the computer cannot pin the miss to a single cylinder. A flashing engine management light with judder means stop driving.

Can I DIY?

Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage.

Caution — conditions applyDIY boundary
ToolsBasic tools only — for example a household socket set, tyre gauge, or a consumer OBD reader.

Some checks may be possible for a careful DIY driver with the right tools and a safe place to work. Stop if anything feels beyond your skill or kit.

P03xxIgnition system and misfire
MOT fail riskif the warning light stays on

What does P0300 mean?

P0300 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 “Random/Multiple Cylinder Misfire Detected”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

How to diagnose P0300 yourself

  1. See if the engine management light flashes: From the driver's seat, note whether the engine management light is steady or flashing, and whether the car judders, shakes, or loses power. Do not clear the code to hide a flashing light. Stop if: The light is flashing, the car judders, fumes enter the cabin, or you cannot pull over safely. Arrange recovery rather than driving on.
    Two panels side by side. On the left, a steady engine management light stays on continuously: limited driving only. On the right, the same light flashes on and off: stop driving and arrange recovery, whether or not you feel judder.
    A flashing engine management light means stop safely and arrange recovery, whether or not you feel judder. A steady light still needs prompt diagnosis, and becomes a stop if it starts to flash, judder or lose power.
  2. Read P0300 and cylinder misfire counts: After the car is stopped in open air, scan for P0300, any P0301–P0308 cylinder codes, freeze-frame, and misfire counters if the reader shows them. Do not swap coils or plugs from this page. Stop if: You would need to idle in a closed garage, the light is still flashing, or you are about to unplug ignition parts.
    Generic driver footwell showing a broad OBD-II socket search zone and the usual 16-pin socket shape.
    Park safely and switch off before locating the socket. Its position varies, so use the vehicle handbook and never force or dismantle trim.

Will P0300 fail an MOT?

An illuminated engine management light is a Major defect at MOT (automatic fail) until the misfire is repaired and the lamp stays off. A misfiring engine can also fail the emissions test or show as visible exhaust smoke.

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.

What the MOT data says

These figures are copied from the MOT fail cohort for the certificate wording below. They are not a diagnosis of this car.

Certificate wording: “Malfunction indicator lamp Engine MIL illuminated indicating a malfunction”.

Of 391,384 Class 4 vehicles that failed a 2024 MOT on that wording, 14.8% (95% CI 14.7–14.9) failed on the same wording again in 2025. The not-tested gap versus control was 11.5 points.

Certificate wording: “Catalyst emissions Lambda coefficient outside the default limits or the range specified by the manufacturer”.

Of 166,607 Class 4 vehicles that failed a 2024 MOT on that wording, 7.5% (95% CI 7.4–7.6) failed on the same wording again in 2025. The not-tested gap versus control was 13.4 points.

Engine management light MOT outcomes

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…
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 P0308Cylinder 8 Misfire Detected

P0300 — quick answers

Is it safe to drive with P0300?

Limited driving only. Limit driving with a steady light and mild roughness. If the engine management light is flashing and the car judders, stop when safe and arrange recovery — continuing can destroy the catalyst.

Can I fix P0300 myself?

Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage. Basic tools only — for example a household socket set, tyre gauge, or a consumer OBD reader.

Will P0300 fail my MOT?

An illuminated engine management light is a Major defect at MOT (automatic fail) until the misfire is repaired and the lamp stays off. A misfiring engine can also fail the emissions test or show as visible exhaust smoke.

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.