P0302 Code: Cylinder 2 Misfire Detected

What Does P0302 Code Mean?

The P0302 diagnostic code indicates that your engine's computer has detected a misfire specifically in cylinder 2. A misfire occurs when the air-fuel mixture in a cylinder fails to ignite properly or doesn't ignite at all. While P0300 indicates random misfires across multiple cylinders, P0302 pinpoints the problem to cylinder 2, making diagnosis more straightforward.

Your engine's crankshaft rotates at a specific speed, and each time a cylinder fires, it momentarily accelerates the crankshaft. The engine control module (ECM) monitors these speed variations. When cylinder 2 fails to fire properly, the ECM detects a momentary slowdown in crankshaft speed at the position corresponding to cylinder 2's firing order. After detecting a certain number of misfires in that specific cylinder, the ECM sets the P0302 code.

Cylinder-specific misfire codes like P0302 typically indicate a problem with components serving that particular cylinder—such as the spark plug, ignition coil, or fuel injector for cylinder 2. Less commonly, mechanical issues like low compression, valve problems, or intake gasket leaks affecting cylinder 2 can cause this code.

Common Causes of P0302

• Bad spark plug in cylinder 2 - Most common cause; worn, fouled, or damaged plug
• Failed ignition coil (cylinder 2) - Coil not delivering spark to that cylinder
• Faulty fuel injector (cylinder 2) - Not spraying fuel properly into cylinder
• Low compression in cylinder 2 - Worn piston rings, valves, or head gasket leak
• Vacuum leak affecting cylinder 2 - Intake gasket leak near that cylinder
• Damaged spark plug wire - If your vehicle uses wires instead of coil-on-plug
• Carbon buildup on valves - Common in direct injection engines
• Faulty wiring to cylinder 2 coil/injector - Electrical connection issues
• Valve timing issues - Bent valve or timing problem affecting cylinder 2

Symptoms You Might Notice

Severity Level: Serious

P0302 is serious severity requiring immediate attention within 24-48 hours. Active misfires send unburned fuel into the exhaust system, which can overheat and destroy your catalytic converter—a $1,000-$2,500 repair. If your check engine light is flashing, severe misfires are occurring and you should stop driving immediately to prevent converter damage.

Continuing to drive with P0302 also causes: raw fuel washing down cylinder walls (stripping protective oil film), increased emissions, dramatic power loss making driving unsafe, and potential damage to engine internals if caused by mechanical issues.

Repair Cost Estimates

Cost-saving strategy: Start with spark plug and coil for cylinder 2 before moving to expensive repairs. Many P0302 cases are resolved with these simple fixes. Always replace all spark plugs together, even if only one cylinder is misfiring.

DIY Fixes vs Professional Help

What You Can Try:

• Replace spark plugs: Moderate difficulty; accessible on most vehicles
• Swap ignition coils: Move cylinder 2 coil to another cylinder; if misfire follows, it's the coil
• Inspect spark plug wires: Look for damage, cracks, or carbon tracking
• Check for vacuum leaks: Spray carb cleaner near intake while engine runs (changes RPM if leak present)
• Scan for other codes: Additional codes provide clues to root cause

When to See a Professional:

• Check engine light is flashing (severe misfires)
• You've replaced spark plugs and coil but code persists
• You suspect compression or mechanical issues
• Need compression testing or fuel injector testing
• Multiple misfire codes present

Affected Car Makes

Ford vehicles with 5.4L and 4.6L engines frequently experience ignition coil failures causing cylinder-specific misfires. Honda and Toyota vehicles commonly see P0302 from worn spark plugs at high mileage. Direct injection engines (many modern vehicles) develop carbon buildup causing misfires.

Related Diagnostic Codes

• P0300: Random/Multiple Misfire - Multiple cylinders misfiring
• P0301, P0303-P0308: Other cylinder-specific misfires
• P0201-P0208: Injector circuit codes for specific cylinders
• P0351-P0358: Ignition coil circuit codes for specific cylinders
• P0420/P0430: Catalyst efficiency - Often damaged by prolonged misfires

Diagnostic Approach

Follow these steps to identify the cause of P0302:

1. Scan for additional codes (injector, coil codes point to specific component)
2. Inspect cylinder 2 spark plug (fouled, worn, or damaged?)
3. Swap cylinder 2 ignition coil with another cylinder
4. Clear codes and test drive; if misfire moves, coil is bad
5. Check compression in cylinder 2 if spark and coil are good
6. Test fuel injector operation and spray pattern
7. Inspect for vacuum leaks affecting cylinder 2