P0204 fault code: Injector Circuit/Open - Cylinder 4

Last updated · OBDCode UK editorial

Can I drive with P0204? — Limit your driving

Our verified driving guidance limits driving for P0204. Use the car only to reach a garage. Stop for a flashing lamp, fuel smell, or if it will not pull cleanly.

P0204 means “Injector Circuit/Open - Cylinder 4” — a fuel and injector circuits fault in the powertrain. Limit your driving. An open injector circuit is stored against cylinder 4. On many four-cylinder engines that is the last hole in the block numbering; the code still does not authorise a parts-cannon injector set.

Can I DIY?

Do not DIY this repair. We do not publish DIY repair or strip-down steps for this code on this page.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.

Do not DIY this repairDIY boundary
ToolsSpecialist tools or workshop equipment — typically a professional garage job.

This fault is in the professional-only category. We do not publish strip-down or fitting steps on this page. Use a qualified garage.

Hot systems

Never open a hot coolant cap — pressure can scald you. Exhaust and catalytic converter get hot enough to burn and ignite debris. Stay clear of electric fans; they can run after shut-off.

P02xxFuel and injector circuits
MOT fail riskif the warning light stays on

What does P0204 mean?

P0204 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P02xx block, which covers fuel and injector circuits. The stored description is “Injector Circuit/Open - Cylinder 4”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0204 fail an MOT?

A lit engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off. Injector-circuit faults are not a DIY MOT ‘clear the lamp’ job.

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

No MOT certificate item corresponds to this code; MOT outcome data cannot be shown.

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.
P0200Injector Circuit/Open P0201Injector Circuit/Open - Cylinder 1 P0202Injector Circuit/Open - Cylinder 2 P0203Injector Circuit/Open - Cylinder 3 P0205Injector Circuit/Open - Cylinder 5 P0206Injector Circuit/Open - Cylinder 6 P0207Injector Circuit/Open - Cylinder 7 P0208Injector Circuit/Open - Cylinder 8

P0204 — quick answers

Is it safe to drive with P0204?

Limit your driving. Our verified driving guidance limits driving for P0204. Use the car only to reach a garage. Stop for a flashing lamp, fuel smell, or if it will not pull cleanly.

Can I fix P0204 myself?

Do not DIY this repair. 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. Specialist tools or workshop equipment — typically a professional garage job.

Will P0204 fail my MOT?

A lit engine management light is a Major defect at MOT (automatic fail) until the fault is repaired and the light stays off. Injector-circuit faults are not a DIY MOT ‘clear the lamp’ job.

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.