All codes
P0303Engine Problems
Cylinder 3 Misfire Detected - Diagnosis Guide
Fix P0303 cylinder 3 misfire code. Learn the common causes and proven solutions for cylinder 3 misfiring.
What you may notice
Symptoms
- 01Check engine light flashing or steady
- 02Rough running engine
- 03Power loss
- 04Increased emissions
- 05Hesitation during acceleration
Where to look first
Common causes
- 01Bad spark plug
- 02Failed ignition coil
- 03Clogged fuel injector
- 04Vacuum leak
- 05Valve train issues
A sensible sequence
Best diagnostic order
- 01Confirm cylinder numbering for the exact engine.
- 02Inspect and swap the spark plug and ignition coil.
- 03Check injector control, intake sealing, and compression.
Step by step
What to check and repair
- 01Replace spark plug in cylinder 3
- 02Swap and test ignition coil
- 03Clean or replace fuel injector
- 04Check for vacuum leaks
- 05Test compression
What Does P0303 Mean?
P0303 indicates that cylinder 3 is misfiring. The ECM detects this by monitoring crankshaft position sensor signals for variations in rotational speed.
Quick Test
Swap the ignition coil from cylinder 3 with another cylinder. If the misfire code changes to follow the coil, replacement is needed.