Engine misfires reduce your engine’s power and can lead to serious complications. The P0302 OBD2 code triggers when cylinder 2 experiences misfires. Knowing which cylinder is having problems is very beneficial when you’re preparing to make repairs.
The P0302 trouble code is potentially quite serious and warrants repair the moment it appears. Read on below to learn more about what this code means and how to diagnose it.
P0302 Code Definition
P0302 Code Definition (Generic): Cylinder 2 Misfire Detected
P0302 BMW: “Misfiring Of Cylinder 2, Damages TWC”
P0302 Dodge: Cylinder 2 Misfire Detected
P0302 Ford Focus: Cylinder #2 Misfire Detected
P0302 Honda: Cylinder 2 Misfire Detected
P0302 Jeep: Cylinder 2 Misfire
P0302 Nissan: Cylinder #2 Misfire Detected
P0302 Toyota: Cylinder 2 Misfire Detected
P0302 VW: Cylinder 2 Misfire
What Does P0302 Mean?
The P0302 OBD2 trouble code triggers when there’s a misfire in your engine. You’ll likely see it along with P0300, which is a more general misfire-related code. P0302 points you to the specific cylinder that’s misfiring: cylinder 2. If you’re not sure which cylinder this is, check your vehicle’s repair manual.
The cylinders are what give your engine its power. Each is topped with a spark plug that ignites the air/fuel mixture in your engine. When your vehicle’s running correctly, each cylinder fires in sequence, providing continuous power to the crankshaft.
If the crankshaft’s RPM changes by more than 2% because of a misfire in cylinder 2, the P0302 trouble code is triggered. You will likely notice significant driving issues if these misfires persist.
What Are The Symptoms Of The P0302 Code?
Engine misfires usually cause significant drivability issues. These symptoms often include:
- Activation of the check engine light. If the light is solid, the change in the crankshaft’s RPM is between 2% and 10%. A blinking or flashing check engine light indicates a change of more than 10%.
- Rough driving. Your car may especially jerk or hesitate when you accelerate. It may also shake or run roughly in other conditions, such as while idling.
- Difficulty starting or failure to start
- Stalling while idling
- Smell of fuel from the exhaust
- Reduced engine power
- Reduced fuel economy
What Are The Causes Of P0302?
The most common causes of a cylinder 2 misfire are:
- Cylinder 2 spark plug is faulty or worn
- Damaged or faulty coils
- Damaged or faulty wires around the spark plugs
- Failed distributor
- Faulty fuel injector
There are other issues that can lead to misfires, including:
- Low fuel pressure
- Leaks in the vacuum system
- Clogged EGR valves, tubes, or ports
- Leaking head gasket
- Malfunction in the fuel system (fuel pump, fuel filter, etc.)
- Defective sensor (camshaft sensor, crankshaft sensor, MAF sensor, oxygen sensor, etc.)
- Fuel quality too low for the system
- Faulty distributor cap or rotor button (if applicable)
How Serious Is The P0302 Code?
The P0302 OBD2 code is very severe. You should not drive your car until you’ve identified the source of the problem. Misfires can cause long-term damage to your catalytic converter and ignition system. The erratic driving they cause also makes your vehicle unsafe to operate.
How To Diagnose The P0302 Code
Tools you’ll need:
- OBD2 scan tool
- Screwdriver and socket set
- Digital multimeter
- Fuel pressure gauge
- Compression tester
- Leakdown tester
- Scan your system for other codes using the OBD2 scan tool. If any other codes come up other than P0300 and other misfire-related codes, fix those first. The other code may be pointing you to the root cause of the misfire.
- Check the wires around the spark plugs to make sure none are loose or damaged. Be sure to also check for loose engine ground wires. Replace or tighten as necessary.
- If your vehicle has individual coil packs in the cylinders, swap the coil from cylinder 2 with the one in cylinder 4. Clear the codes and test drive your car. If the misfire moves to cylinder 4, replace the coil pack.
- Visually inspect the cylinder 4 spark plug with a new spark plug on-hand for comparison. If the plug looks dirty or has carbon build-up, remove and clean it.
- Test the resistance of the spark plug wires using a multimeter. The typical resistance is between 10,000 and 15,000 ohms. You can find the specific resistance in your vehicle’s manual. If the resistance is higher, replace the wire.
- Use a multimeter to test the ignition coils. Remove the coil and touch the leads of the multimeter to both the primary and secondary ignition circuits. The primary ignition circuit should read between .4 and 2 ohms, and the secondary between 6,000 and 10,000 ohms. A 0 reading on either indicates an internal short.
- Test your fuel system using a fuel pressure gauge. The correct readings for your engine should be listed in your manual.
- Use a multimeter to check the fuel injectors. First, unplug the injector from the engine, then use the multimeter leads to probe the terminals. Check your vehicle manual for the correct resistance.
- Perform a leak down test and an engine compression test. Mechanical problems can often lead to engine misfires. Common things to look for are a burned valve, a broken piston ring or valve spring, a worn valve guide, or skipped teeth on the timing chain.
Common Mistakes To Avoid While Diagnosing The P0302 Code
It’s easy to overlook small issues like a broken wire or a loose electrical connection. Be thorough in the inspection of your engine. If you’re lucky, you’ll only need to make a minor repair.
What Should You Do To Fix The Code P0302?
If you’re not experiencing any drivability issues, clear the trouble code. A single misfire may not be cause for significant concern. Take a test drive to see if the code comes back. If it does, continue with the steps below.
- Replace any damaged wires, connectors, or tabs found in your inspection.
- Replace any components that failed the diagnostic tests above.
- Clean the fuel injectors using a fuel injector cleaning kit. You can find these at any auto parts store.
- If the problem persists, test your engine’s sensors, including the crankshaft sensor, camshaft sensor, oxygen sensors, and MAF sensor. Replace or clean them as necessary.
Tips To Avoid P0302 In The Future
Replacing your ignition system’s minor components as part of your regular maintenance can prevent problems before they occur. Verify the recommended lifespan of your spark plugs, rotor, and distributor cap. Replace them before they’ve exceeded this lifespan.