Motor Vehicle Expert
OBD fault code guide

P0201 Code Meaning UK

P0201 means “Injector Circuit/Open Cylinder 1”. In plain English, the engine computer has detected an electrical problem with the fuel injector circuit for cylinder 1. It may be a faulty injector, damaged wiring, loose connector, poor power supply, bad earth, short circuit, open circuit or ECU injector driver issue.

📅 Updated June 2026 🇬🇧 UK diagnostic guide 🛠 Injector circuit fault
Quick answer Fault codes hub Related misfire code
✓ P0201 meaning ✓ Injector causes ✓ UK repair costs ✓ MOT-aware advice
Quick answer Meaning Symptoms Causes Diagnosis Repair costs Can you drive? MOT impact Related guides FAQs
Quick answer

What does P0201 mean?

P0201 means there is a problem with the injector circuit for cylinder 1. The injector is responsible for delivering fuel into that cylinder. If the injector circuit is open, shorted, poorly connected or not being controlled correctly, cylinder 1 may not receive fuel properly. That can cause misfires, rough running, poor starting, smoke, fuel smell or loss of power.

Most likely area

Cylinder 1 injector, injector wiring, connector, power supply, earth, ECU driver or injector control circuit.

Urgency

High if the car misfires, shakes, smells of fuel, loses power or has a flashing engine light.

MOT risk

Can affect emissions, engine warning light status, smoke levels and running quality.

Code meaning

P0201 — Injector Circuit/Open Cylinder 1

The full description is usually P0201 Injector Circuit/Open Cylinder 1. This is not simply saying “replace injector 1”. It means the ECU has detected an electrical fault in the injector circuit for cylinder 1.

The fault could be inside the injector, but it could also be in the wiring loom, connector, power feed, ground/control side or ECU driver. On modern vehicles, especially diesels and direct-injection petrol engines, injector diagnosis needs to be done carefully because injectors can be expensive and may need coding.

Mechanic view

Why P0201 needs proper testing

A common mistake is replacing injector 1 straight away. Sometimes the injector is faulty, but a broken wire, corroded plug, loose connector or ECU control issue can trigger the same code.

The correct approach is to test the injector circuit first. If the injector is replaced without checking the wiring, the fault can come straight back and the customer has paid for an expensive part unnecessarily.

Symptoms

Common symptoms of a P0201 code

P0201 often causes noticeable running problems because one cylinder may not be receiving fuel correctly.

Engine management light

A steady or flashing engine warning light may appear depending on how badly the fault affects the engine.

Misfire or shaking

The engine may shake, judder or idle roughly if cylinder 1 is not fuelling properly.

Poor starting

An injector circuit fault can cause long cranking, hard starting or unstable running after start-up.

Loss of power

The car may feel weak, sluggish or go into limp mode to protect the engine and emissions system.

Fuel smell or smoke

Poor injector control can cause unburnt fuel, smoke or a strong fuel smell.

Poor fuel economy

Incorrect fuelling can reduce efficiency and increase fuel use.

Common causes

What causes a P0201 fault code?

P0201 is usually an electrical injector circuit problem, but mechanical injector faults can also be involved.

Very common

Faulty cylinder 1 injector

The injector coil or internal electrical circuit may fail, causing an open or short circuit.

Wiring

Broken injector wire

A damaged wire in the injector loom can stop the injector receiving or returning the correct signal.

Connector

Loose or corroded injector plug

Injector connectors can become loose, oil-contaminated, corroded or damaged by heat and vibration.

Circuit

Open circuit

A break in the wiring or injector coil can stop the circuit completing properly.

Circuit

Short circuit

A wire shorting to ground or power can trigger injector circuit codes and may blow fuses.

Power supply

Injector power feed fault

A shared injector feed or relay problem can affect injector operation.

ECU control

ECU injector driver fault

Less common, but the ECU driver controlling cylinder 1 injector can fail.

Diesel system

Injector coding or control issue

Some diesel injectors require coding or adaptation after replacement.

Mechanical

Injector mechanically stuck

An injector can fail mechanically as well as electrically, causing misfire or poor fuelling symptoms.

Diagnosis

How a garage should diagnose P0201

✅ Scan all stored, pending and permanent codes.

✅ Record freeze frame data before clearing anything.

✅ Check for misfire codes such as P0300 or cylinder-specific codes.

✅ Confirm which cylinder is cylinder 1 for the engine layout.

✅ Inspect the cylinder 1 injector plug and wiring loom.

✅ Check injector resistance where manufacturer data is available.

✅ Check injector power feed and ECU control signal.

✅ Check for open circuits, short circuits and poor earth/control side issues.

✅ On diesel vehicles, check whether injector coding or specialist testing is required.

Avoid this mistake

Do not guess the injector

P0201 points to cylinder 1 injector circuit, but it does not prove the injector itself is bad. If the plug is loose or the loom is broken, a new injector will not fix it.

On some vehicles, swapping injectors without coding or proper testing can create more problems. The safest route is to prove whether the fault follows the injector, stays with the wiring, or comes from the ECU control side.

UK repair cost guide

How much does P0201 cost to fix in the UK?

Costs vary by petrol or diesel engine, injector access, whether coding is required, parts quality and labour rate. These are rough UK guide prices only.

Diagnostic scan and circuit test

Usually around £40–£120 depending on how much injector circuit testing is included.

Connector or wiring repair

May be moderate cost if accessible, but loom faults can take time to trace.

Petrol injector replacement

Can be moderate depending on access and whether the injector is easy to remove.

Diesel injector replacement

Can be expensive due to injector cost, coding, access and possible seized injectors.

Injector coding or adaptation

Some diesel injectors need coding after replacement so the ECU can control them correctly.

ECU driver diagnosis

Less common, but can become expensive if ECU testing or repair is needed.

Safe driving advice

Can you drive with a P0201 code?

P0201 should be treated seriously. If the engine is misfiring, shaking, smoking, smelling of fuel or the engine light is flashing, avoid driving. Unburnt fuel can damage the catalytic converter, and poor injector control can make the car unreliable.

✅ Lower risk: stored code only, steady engine light, no misfire and normal performance.

⚠️ Medium risk: rough idle, poor starting, poor economy or occasional hesitation.

🚫 High risk: flashing engine light, strong misfire, fuel smell, smoke, limp mode or major loss of power.

Real experience

What I would check first

On a real car with P0201, I would first inspect the cylinder 1 injector connector and wiring. Injector plugs can be disturbed during servicing, engine work or previous repairs.

Then I would check whether the injector is receiving power and whether the ECU is controlling it. If the wiring checks out, injector resistance and injector operation become the next focus. On diesels, I would be careful about removal and coding before fitting anything.

MOT implications

Will P0201 fail an MOT?

P0201 can lead to an MOT failure if it causes an emissions-related engine warning light, rough running, misfire, visible smoke, fuel smell or poor emissions. A faulty injector circuit can stop one cylinder fuelling correctly, which can affect combustion and exhaust readings.

Misfire risk

Injector faults can cause misfires, which may increase emissions and damage the catalyst.

Warning light issue

An engine warning light linked to emissions should be investigated before MOT.

Smoke or fuel smell

Smoke, fuel smell or rough running should be repaired before presenting the vehicle for MOT.

Engine light MOT guide Common MOT failures
Back to main hub

Browse more OBD fault code guides

P0201 is one common injector circuit and misfire-related diagnostic trouble code. For more common codes, meanings, symptoms, repair costs and MOT implications, use the main Motor Vehicle Expert fault-code hub.

Back to OBD Fault Codes Hub Use Diagnostic App
Frequently asked questions

Frequently Asked Questions About P0201

Find answers to common questions about P0201 injector circuit faults, driving safety, repair costs and MOT implications.

What does P0201 mean?

P0201 means the engine computer has detected a fault in the injector circuit for cylinder 1. This can be caused by the injector itself, wiring, connector problems, poor power supply, poor ground or an ECU injector driver issue.

Can I drive with a P0201 code?

You should be careful driving with P0201. If the engine is misfiring, shaking, smells of fuel, has poor power or the engine light is flashing, avoid driving because unburnt fuel can damage the catalytic converter.

Will P0201 fail an MOT?

P0201 can lead to an MOT failure if it causes an emissions-related engine warning light, misfire, rough running, smoke, fuel smell or poor emissions during the test.

What causes a P0201 code?

Common causes include a faulty cylinder 1 injector, injector wiring fault, corroded connector, open circuit, short circuit, poor power supply, poor earth, ECU injector driver fault or mechanical injector failure.

How much does P0201 cost to fix in the UK?

A diagnostic check may cost around £40 to £120. Wiring or connector repairs may be moderate, while injector replacement, coding or diesel injector work can cost significantly more depending on the vehicle.

Is P0201 the same as a misfire code?

No. P0201 is an injector circuit fault for cylinder 1, while misfire codes such as P0300 or P0301 relate to combustion misfires. However, an injector circuit fault can cause a misfire.

About this guide

Based on practical mechanic-style diagnostic experience

Motor Vehicle Expert publishes practical UK vehicle guidance based on real-world mechanical knowledge and hands-on diagnostic experience. This P0201 guide is written to help drivers understand injector circuit faults before replacing expensive injectors unnecessarily.

Fault codes should always be treated as a starting point for diagnosis. If your car has a flashing engine light, severe misfire, smoke, strong fuel smell, overheating or major power loss, stop driving and get professional help.