Code P0300 means misfires have been detected on several cylinders or at random. If the check engine light flashes it is urgent: unburned fuel can damage the catalytic converter.
What code P0300 means
Random or multiple cylinder misfire.
Typical symptoms
- Rough running and vibration
- Jerking and loss of power
- Check engine light on or flashing
- Smell of unburned fuel
- Higher fuel consumption
Most likely causes
| Cause | How common | What to do |
|---|---|---|
| Worn spark plugs or coils | Very common | Replace plugs and coils |
| Intake leaks | Common | Leak test and repair |
| Dirty or faulty injectors | Common | Test and replace |
| Contaminated fuel or low pressure | Common | Check fuel and pump |
| Low compression or mechanical issues | Less common | Compression test |
| EGR valve or sensors | Less common | Check and clean |
How it is diagnosed
- Read misfire counters for each cylinder.
- Check plugs, coils and injectors.
- Intake leak test.
- Compression test if necessary.
Can you drive with code P0300?
With a steady light you can carry on with care and for short trips. If the light flashes, stop: the catalytic converter may be damaged.
How much does it cost to fix?
| Work | Indicative cost |
|---|---|
| Spark plugs (set) | €40-150 |
| Coil (each) | €40-150 |
| Injector cleaning / replacement | €150-400 each |
| Mechanical repair | on quote |
Figures are indicative market ranges, useful for orientation: the real cost depends on model, engine, parts chosen and labour hours. For an exact quote we need the vehicle registration number.
How MasterTuning helps
We read the real values of the control unit, not just the code: that is the difference between finding the faulty component and replacing parts by trial and error. After the repair we clear the error and check that it does not come back. Find the nearest centre or contact us.
Got code P0300 on your car? Book a diagnosis at the nearest MasterTuning centre.
Frequently asked questions
What does P0300 mean?
Random or multiple cylinder misfires.
What does a flashing light mean?
That the misfire is significant and unburned fuel can damage the catalytic converter: act immediately.
Are P0300 and P0301-P0304 related?
Yes: P0300 is general, while P0301-P0304 point to the specific cylinder.
How much does it cost to fix P0300?
From €40-150 for plugs to €150-400 per injector: diagnosis decides.
