⚡ AUTO CODE FIX
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EngineCritical✅ DIY Friendly

P0304

Cylinder 4 Misfire Detected

Misfire in cylinder 4. If coolant level is dropping without visible leak, suspect head gasket failure.

SeverityCritical
CategoryEngine
Est. Repair Cost$50–$500
Code TypePowertrain
DIY RepairYes

⚡ Common Causes

⚠️ Symptoms

✅ How to Fix — Step by Step

  • Step 1:Inspect and replace spark plug
  • Step 2:Swap and test coil
  • Step 3:Replace injector if no pulse
  • Step 4:Check for coolant in oil — possible head gasket
💡 Pro Tip: If coolant level drops without a visible leak, suspect head gasket failure alongside the misfire.

Repair Cost Estimate

Full Repair Estimate
$50–$500
DIY Possible?
YES
Severity
Critical

Frequently Asked Questions

What does OBD2 code P0304 mean?+
P0304 stands for Cylinder 4 Misfire Detected. Misfire in cylinder 4. If coolant level is dropping without visible leak, suspect head gasket failure.
What causes code P0304?+
Fouled spark plug; Failed ignition coil; Injector clog; Cracked piston ring or head gasket failure
How do I fix code P0304?+
Inspect and replace spark plug; Swap and test coil; Replace injector if no pulse; Check for coolant in oil — possible head gasket
How much does it cost to fix P0304?+
Estimated repair cost for P0304 is $50–$500.
Is P0304 DIY-friendly?+
Yes — P0304 is generally DIY-friendly with basic tools.

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