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Fault code P0304 means misfires on cylinder 4. Irregular combustion localised on the fourth cylinder.

Typical symptoms

• Vibration and jerking
• Loss of power
• Engine light on or flashing

Most common causes

• Cylinder 4 spark plug or coil
• Failed injector
• Low compression
• Localised intake leak

How it is checked in diagnosis

• Swapping components between cylinders
• Compression and leak-down test
• Reading the misfire counters

Can you drive with code P0304?

With a flashing light no.

How MasterTuning helps

We read the real values from the ECU, not just the code: that is the difference between identifying the component responsible and replacing parts by trial and error. After the repair we clear the fault and check that it does not come back. Centres throughout Italy.

Read more: vehicle database · find an installer · what is ECU remapping

Do you have code P0304 on your car? Book a diagnosis at your nearest MasterTuning centre.

Frequently asked questions

What does fault code P0304 mean?

Code P0304 means misfires on cylinder 4. Irregular combustion localised on the fourth cylinder.

Can you drive with fault P0304?

With a flashing light no.

Is clearing code P0304 enough to fix it?

No: if the cause is still present the code comes back after a few kilometres. Clearing should only be done after the repair, with the diagnostic tool.

How much does it cost to fix code P0304?

It depends on the component responsible: the diagnosis is precisely what identifies it with real measurements, avoiding unnecessary replacements that cost far more than the correct repair.