Quick answer: The P0302 code indicates that your vehicle’s engine control module has detected repeated misfires in cylinder number two. This directly affects the ignition and combustion system. You should address this promptly to prevent unburned fuel from damaging your catalytic converter, which is a highly expensive component to replace.
Seeing a flashing or solid check engine light can be stressful, especially when your scan tool reveals a P0302 code. This diagnostic trouble code points to a specific issue in your engine’s combustion process that causes rough running. In this guide, we will break down what causes this misfire, how you can diagnose it at home, and what it costs to fix.
What Does P0302 Mean?
Inside your engine, the computer monitors the speed of the crankshaft to ensure every cylinder fires smoothly and on time. If cylinder number two fails to ignite its fuel-air mixture properly, the crankshaft momentarily slows down. The computer detects this drop in speed, recognizes that cylinder two is the culprit, and triggers the P0302 code to help you pinpoint the issue.
Symptoms
- Rough idling or engine shaking
- Loss of engine power, especially under acceleration
- A flashing or solid check engine light
- Hesitation or jerking while driving
- A strong smell of unburned fuel from the exhaust
- Decreased fuel economy
Possible Causes
Many DIYers rush to buy a new ignition coil or fuel injector immediately, which can waste money if the issue is just a worn spark plug or a simple vacuum leak.
- Worn or fouled spark plug in cylinder 2
- Damaged or failing ignition coil or spark plug wire
- Vacuum leak near the cylinder 2 intake runner
- Failing fuel injector or wiring harness issue
- Low engine compression in cylinder 2 due to worn valves or rings
Check These Yourself Before Visiting a Mechanic
- Inspect the ignition coil wiring and connector at cylinder 2 for loose pins, corrosion, or cracks.
- Perform a coil swap test: swap the ignition coil from cylinder 2 to cylinder 1, clear the code, and see if the misfire code changes to P0301.
- Look for loose, cracked, or disconnected vacuum hoses around the intake manifold that could cause unmetered air to enter.
How to Fix It
- Scan the vehicle to confirm P0302 is the only active code.
- Inspect and replace the spark plugs if they are worn or fouled.
- Swap the ignition coil to another cylinder to isolate if the misfire follows the coil. Replace the coil if the code moves.
- Inspect the fuel injector connector and test the injector’s resistance and pulse.
- Perform a smoke test to identify any vacuum leaks affecting cylinder 2.
- Run a compression and leak-down test on cylinder 2 to check for internal mechanical damage.
Estimated Repair Costs (2026)
| Job | Parts ($) | Labor ($) |
|---|---|---|
| Spark Plug Replacement (Single) | $10 – $25 | $50 – $100 |
| Ignition Coil Replacement | $40 – $120 | $60 – $120 |
| Vacuum Leak Repair | $10 – $80 | $100 – $200 |
| Fuel Injector Replacement | $80 – $250 | $120 – $250 |
| Engine Compression Repair (Valves/Rings) | $300 – $1,000 | $1,200 – $3,000 |
Note: these are 2026 estimates in US dollars; costs vary by make and model.
Frequently Asked Questions
Can I drive with the P0302 code?
You should avoid driving with an active misfire code, especially if the check engine light is flashing. A flashing light indicates that raw, unburned fuel is entering the exhaust system, which can quickly overheat and destroy your catalytic converter, leading to much higher repair bills.
How do I clear the P0302 code?
Once you have identified and repaired the underlying cause, you can clear the code using an OBD-II scanner. Alternatively, the engine computer will clear the code on its own after a few drive cycles if it detects that cylinder two is firing normally again.
Why is my car shaking when the P0302 code is active?
Your engine relies on a balanced cycle of combustion across all cylinders. When cylinder two fails to fire, it creates an uneven power stroke, causing the engine to lose balance and produce noticeable vibrations or shaking, particularly when idling at a stoplight.