TorqueMech Diagnostic Guide
P0303 — Cylinder 3 Misfire Detected
Diagnostic checks and likely repair paths for a cylinder 3 misfire.
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What It Means
The powertrain control module detected a misfire on cylinder 3.
Inspection Priority
- Inspect ignition components first when misfire evidence is present.
- Verify fuel trim behavior before replacing parts.
- Check for vacuum leaks when misfires are random or lean-related.
Common repair when plug wear or coil failure is confirmed.
Multiple causes possible when misfire counters move between cylinders.
Further diagnostics may be required if fuel trim or compression clues do not match ignition faults.
Common Causes
- Faulty spark plug
- Faulty ignition coil
- Fuel injector issue
- Compression problem
- Vacuum leak near affected cylinder
- Coolant intrusion or head gasket issue
Quick Checks
- Inspect spark plug condition
- Swap ignition coil with another cylinder if applicable
- Inspect injector connector and function
- Check compression
- Look for coolant loss or signs of internal leak