#OBD Codes
P0302 – Cylinder #2 misfire detected
Technical definition
Cyl. 2 misfire detected
What does P0302 mean?
Diagnostic trouble code P0302 means there’s a problem with cylinder number 2 in your engine – meaning it’s not working properly, which is called a “misfire.”
Each engine manufacturer has its own rules for cylinder numbering. Generally, the first cylinder is closest to the front of the engine (drive belt or chain), and the second is usually the next in line.
On V-shaped engines – common in larger or more powerful vehicles, like sports cars, trucks, or some BMW and Chevy models – the second cylinder might be on the opposite side. It’s always best to refer to your vehicle’s manual for the exact numbering to be sure.
A misfire happens when the air and fuel in a cylinder don’t burn (or don’t burn completely) during the combustion process, so it’s incomplete. Misfires can result from problems with the ignition system, fuel system, or mechanical components.
Incomplete combustion can lead to issues such as the check engine light turning on, reduced engine power, and increased emissions, which could cause your vehicle to fail an emissions test.
Misfires can be intermittent or continuous. Intermittent misfires are harder to spot and diagnose without a diagnostic tool, whereas continuous misfires are usually obvious and can feel like the engine is running roughly.
How serious is the P0302?
The P0302 code requires immediate attention because failing to address it early can lead to bigger problems down the road. Here’s why:
First, when a cylinder misfires, the engine burns fuel inefficiently, reducing your car’s fuel economy and increasing harmful emissions.
Moreover, persistent misfires can damage the catalytic converter, which is a very expensive component to replace. How it happens: when a misfire occurs, unburned fuel enters the exhaust system, where it ignites due to high temperatures and creates extreme heat. This intense heat can melt the ceramic core of the catalytic converter – leaving it useless.
Finally, engine misfires can also lead to engine knocking or pinging. These issues put extra strain on internal components like pistons and valves, increasing the risk of long-term engine damage.
Can I still drive with P0302?
While you may still be able to drive with a P0302 code, you should avoid doing so.
It's dangerous to ignore the P0302 code because misfires can reduce engine performance. You might experience a rough idle, poor acceleration, and reduced fuel efficiency. This not only makes driving unpleasant but also puts you in risky situations – like struggling to merge onto highways or pass other vehicles.
Sometimes, your vehicle may activate a self-preservation mode, commonly known as limp mode. This safety feature reduces engine power to prevent further damage. While it’s useful in emergencies, driving in limp mode can be difficult, so it’s best to do so only to reach the nearest repair shop.
It's essential to address the problem as soon as possible to save yourself from headaches and, of course, expenses. Timely repairs can prevent further engine damage and ensure your vehicle runs smoothly.
Common symptoms of P0302
Symptoms associated with the P0302 code include:
- Check engine light turn on
- Rough idle
- Unusual engine noises, such as knocking or pinging
- Poor acceleration
- Reduced fuel efficiency
Common causes of P0302
Ignition system issues
- Faulty spark plug or spark plug wire on cylinder no. 2
- Worn or damaged ignition coil on cylinder no. 2
- Incorrect ignition timing
Fuel system issues
- Dirty fuel filter
- Clogged fuel injector on cylinder no. 2
- Faulty fuel pump
Mechanical issues
- Damaged valve on cylinder no. 2
- Damaged cylinder no. 2 walls
- Worn piston rings in cylinder no. 2
Air intake issues
- Vacuum leak in the intake manifold or vacuum hoses
Circuit issues
- Crankshaft or camshaft position sensor problems
- Faulty oxygen (O2) sensor
Other issues
- Poor fuel quality
- Incorrect engine chip tuning
- Malfunctioning EGR valve or clogged EGR passages
How to troubleshoot P0302
Use these tips to diagnose and fix a P0302 code accurately:
Scan fault codes
Start by using an OBD scan tool to look for any other related trouble codes, which may provide additional clues to the underlying problem – misfire in cylinder 2. These faults include:
- P0100-P0104: Mass Air Flow (MAF) sensor-related codes that indicate sensor problems affecting the air-fuel mixture
- P0130-P0167: Oxygen sensor-related codes that might signal problems with the sensors responsible for monitoring the air-fuel ratio
- P0300-P0312: These codes identify misfiring cylinders. The last two digits indicate the cylinder (e.g., P0301 for cylinder 1), while P0300 indicates multiple cylinders misfiring. This helps identify if the issue is cylinder-specific (e.g., bad spark plug) or affects all cylinders (e.g., low fuel pressure).
- P0335-P0339: Crankshaft position sensor trouble codes that could affect ignition timing
- P0351-P0362: Ignition coil issues, which might mean one or more coils aren’t delivering spark properly
Clear the codes and test drive
Use your scan tool to clear the fault codes.
- If the fault codes immediately reappear: This indicates the issue is ongoing. Skip the test drive and continue troubleshooting other potential causes.
- If the codes clear successfully: Drive your car for about 15 minutes to fully warm up the engine and observe its behavior.
After the test drive, perform another scan to see if the code reappears. If it does, this confirms the problem persists and requires further investigation.
Check freeze frame data
The freeze frame data provides a snapshot of your car’s engine conditions at the exact moment when a fault code occurred. This data may include parameters such as engine load, temperature, RPM, and other factors that help you understand the conditions that triggered the code.
Why does it matter?
It can show whether the misfire happened while idling, accelerating, or under high load. Plus, it helps identify if the issue is linked to a cold or warm engine.
For example, if the misfire occurred during high RPMs, it might suggest fuel delivery issues like a failing pump or clogged injectors. If it happened at idle, the cause could be an ignition problem or a vacuum leak.
Analyze misfire counter live data readings
Live data tools, like OBDeleven, allow you to monitor real-time misfire counter readings for each cylinder. For Volkswagen Group vehicles, you can find these values in the engine control unit details:
OBDeleven live data feature
The misfire counter tracks the number of misfires detected in each cylinder.
What to look for:
- Misfire frequency: If cylinder 2 shows a higher misfire count compared to others, it pinpoints the affected area.
- Driving conditions: Misfires occurring during high engine load could indicate insufficient fuel pressure, while misfires at idle may point to ignition or mechanical issues.
Pro tip: Use live data to test specific scenarios. For example, monitor the misfire counter while accelerating hard or idling to recreate the conditions that trigger the code.
Further reading: How to read OBD live data
Check other live data parameters
Other related live data parameters can also help identify potential causes of the P0301 code. Consider looking at:
- Fuel trim readings (short-term and long-term). Fuel trim readings show how the engine adjusts the air-fuel mixture. High positive values mean it's too lean (not enough fuel), and high negative values mean it's too rich (too much fuel). Normal values usually range between -5% and +5%.
- Ignition timing. Monitor the ignition timing angle to ensure it remains within the appropriate range, which depends on various factors. You can learn more about ignition timing here.
- Mass Air Flow (MAF) sensor readings. Make sure the MAF sensor is providing accurate airflow readings. Abnormally high or low readings may indicate sensor issues or intake air leaks.
- Oxygen sensor voltage. Check the upstream O2 sensor (closest to the engine) for proper operation, which typically fluctuates between 0.1 and 0.9 volts. Consistently low or high readings can indicate air-fuel mixture problems.
- Engine speed (RPM). Consistent and stable RPM readings indicate engine works properly. Fluctuations or sudden drops in RPM can signal misfiring or broader engine performance issues.
Inspect and replace spark plugs regularly
Check the spark plugs’ condition and replace them if worn out or damaged. In normal conditions, spark plugs last from 50,000 to 160,000 kilometers (30,000 to 100,000 miles).
If all the spark plugs look good, check the spark plug boots and spark plug wires. The rubber tends to deteriorate over time, resulting in increased electrical resistance or cracks in the insulation.
Test the ignition coil packs
To pinpoint a failed coil pack, you'll need a multimeter. Follow these steps:
- Set the multimeter to measure resistance (Ω)
- Test the resistance between the coil terminals
- Compare the reading to your vehicle’s specified range (found in the manual)
If the reading is zero or falls outside the recommended range, the coil pack may need replacing. Faulty ignition coils can cause misfires, reduced engine performance, and increased emissions.
Pro tip: Not all ignition coils are the same. You can check how to test different types of ignition coils in this video.
Check the fuel system
Test the fuel pressure using a fuel pressure gauge to ensure it meets the manufacturer's specifications. If the pressure is too low, inspect the fuel pump, fuel filter, and fuel injectors for issues, as any of these components can disrupt the air-fuel mixture, causing misfires or reduced engine performance.
Inspect for vacuum leaks
Inspect the intake manifold, hoses, and gasket for any signs of cracks, holes, or loose connections. You can also use a smoke machine to pinpoint hard-to-spot leaks – smoke will escape from the leak points, making them easy to find.
Another method is to spray a small amount of carburetor cleaner around suspect areas while the engine runs. If the engine's idle speed changes, this might mean a vacuum is leaking.
Perform a compression test
Check the compression in each cylinder to ensure it meets the manufacturer's specifications. Low compression can signal mechanical issues like bent valves, a blown head gasket, or worn piston rings.
How to perform a compression test:
- Remove all spark plugs
- Insert a compression gauge into one cylinder at a time
- Crank the engine and record the pressure reading for each cylinder
Once you’ve tested all the cylinders, compare the results to the manufacturer’s specifications:
- Low compression in particular cylinder often points to issues like a bent valve or a blown head gasket
- Low compression in all cylinders may indicate worn piston rings
Engine compression measurement. Source: autozone.com
FAQ
How much does it cost to fix a P0302 code?
Fixing a P0302 code can range from as little as $25 for a new set of spark plugs to several thousand dollars for major repairs, such as an engine rebuild required due to worn piston rings or bent valves. The exact cost depends on the underlying cause and the extent of the damage.
Can a clogged fuel filter or dirty air filter cause a P0302 misfire code?
Yes, a clogged fuel filter can restrict fuel flow to the engine, causing the vehicle to run lean. Similarly, a dirty air filter can restrict airflow and make the air-fuel mixture too rich, which can prevent proper ignition and cause misfires.
How do camshaft and crankshaft position sensors affect misfires?
Camshaft and crankshaft position sensors provide critical information about their position and speed to the powertrain control module (PCM). When these sensors malfunction, it can lead to improper fuel injection and ignition timing.
Disclaimer: Advice, how-to guides, and car care tips on our blog are intended as helpful resources for general maintenance and repairs. While we strive for accuracy, the information is provided to the best of our knowledge and should be used at your own discretion and risk.
Always refer to your vehicle's owner's manual or consult a certified mechanic for specific repair details and safety procedures.
Always refer to your vehicle's owner's manual or consult a certified mechanic for specific repair details and safety procedures.