Misfire · Fault code
P0300
Random / Multiple Cylinder Misfire
The ECU detected misfires but could not attribute them to one cylinder. "Random" means unattributed, not that every cylinder is failing.
Severity EXPERT Moderate — diagnose before it gets worse
Driveability EXPERT Drive with caution — the ECU is already protecting itself
Tuning EXPERT Diagnose first — do not tune onto this
Check first — in this order
The order is the product. A list of "possible causes" is what every parts site publishes, and it is why people replace parts blindly.
- Read per-cylinder misfire counters first. If one cylinder dominates, this is really a P030x and the diagnosis narrows immediately. EXPERT
- Read the conditions it logs under from freeze frame — cold-and-idle only points somewhere different from misfire under load. EXPERT
- On a direct-injection turbo petrol, check ignition coils and spark plugs early — the most common single cause and cheap to exclude. EXPERT
- Check for unmetered air and fuel delivery under load, and read fuel trims — a lean misfire and a mechanical one diverge here. EXPERT
What this code does not license you to replace
- That all cylinders are bad. The ECU could not attribute the misfire, which is not the same as everything failing.
- That coils are the cause before the conditions and the fuelling have been read.
Companion codes
Codes whose presence alongside P0300 changes the path.
Built by DMS Tuned
Stuck on P0300? Send us the log.
DMS Tuned is a real ECU-tuning shop. If you have a boost/requested-vs-actual log, run it through the analyser first — then message us and we will read it with you before you spend money on parts.
Ask the engineers on WhatsApp →Advertising content · DMS Tuned serves Greece and remote where legal. We never sell a tune onto an un-diagnosed fault.