P0303

Q: What does OBD2 code P0303 mean?

P0303 means: Cylinder 3 Misfire Detected. Misfire detected in cylinder 3. On direct injection engines, carbon buildup on intake valves is a common cause.

Cylinder 3 Misfire Detected

Misfire detected in cylinder 3. On direct injection engines, carbon buildup on intake valves is a common cause.

SeverityCritical

CategoryEngine

Est. Repair Cost$50–$400

Code TypePowertrain

DIY RepairYes

⚡ Common Causes

›Bad spark plug
›Coil failure
›Fuel delivery issue to cylinder 3
›Carbon buildup on intake valves (GDI engines)

⚠️ Symptoms

›Shaking at idle
›Hesitation under acceleration
›Fuel odor from exhaust
›Poor MPG

✅ How to Fix — Step by Step

Step 1:Replace spark plug
Step 2:Replace coil pack
Step 3:Check injector flow
Step 4:Perform walnut blasting on intake valves if GDI engine

💡 Pro Tip: GDI engines are prone to intake valve carbon buildup — not cleaned by fuel additives alone.

Repair Cost Estimate

Full Repair Estimate

$50–$400

DIY Possible?

YES

Severity

Critical

Frequently Asked Questions

What does OBD2 code P0303 mean?+

P0303 stands for Cylinder 3 Misfire Detected. Misfire detected in cylinder 3. On direct injection engines, carbon buildup on intake valves is a common cause.

What causes code P0303?+

Bad spark plug; Coil failure; Fuel delivery issue to cylinder 3; Carbon buildup on intake valves (GDI engines)

How do I fix code P0303?+

Replace spark plug; Replace coil pack; Check injector flow; Perform walnut blasting on intake valves if GDI engine

How much does it cost to fix P0303?+

Estimated repair cost for P0303 is $50–$400.

Is P0303 DIY-friendly?+

Yes — P0303 is generally DIY-friendly with basic tools.