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P0301 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition and Meaning

A P0301 trouble code indicates that your vehicle’s cylinder number 1 is misfiring. These are among the most common types of OBD codes. This happens when the cylinder isn’t receiving enough fuel to function properly. As a result, the engine will not run due to a lack of fuel combustion. A dysfunctional ignition and/or fuel system can be a direct cause of the misfire. A P0301 code is one that should be taken seriously, as engine misfires can cause serious long-term damage to your vehicle. Faulty spark plugs and wiring can also be a factor when dealing with this code.


Again, your ignition and fueling systems should be where you check first when getting a code P0301. Check your spark plugs, coil packs, and exhaust valves as well. Sensors are another potential source as well. This includes camshaft, crankshaft, mass airflow and oxygen sensors.


So, what are the symptoms of a code P0301? For starters, your check engine light will come on or start flashing. You’ll also be able to identify issues while you drive, as the engine will run a little rough and start to shake. Starting the car might also be troublesome and the engine could rumble. If the car doesn’t accelerate smoothly, you may be having misfiring issues.


Start by scanning your vehicle’s codes here’s a great one we use everyday. Also, be sure to check your ignition coils for loose connectors as well as any kind of wiring damage. These can be common causes for misfires. Check your spark plugs as well. If there are issues with any of those, consider replacing them.

Once replaced, take the car for a road test and scan the codes again. If you don’t experience the same issues while driving and you no longer have the same error code, problem solved. If the ignition system is ok and the problems still reside elsewhere, you’ll want to look at your fuel system. Pay extra attention to your fuel pressure and fuel injectors as these are the more common causes. Leaky gaskets, faulty valve springs and damaged piston rings can also create issues. As mentioned before, misfiring can come from a variety of problems, so be sure to do a thorough inspection of your vehicle and engine.

Common mistakes

One of the most common mistakes made is not performing any kind of visual inspection of the fuel injector wiring. Doing this can save you the time and money that would go into replacing spark plugs among other things. Disconnected vacuum hoses are also something that tends to be overlooked.

Other similar codes to P0301 (P0302 and P0303, for example) have very similar issues as well. Completing a proper diagnostic test based on symptoms of those codes should also be done.

How serious is this?

A code P0301 should be taken very seriously and acted upon with urgency. Serious long-term damage can result from consistent engine misfiring, so don’t hesitate to get this problem resolved.

It’s also dangerous to drive when dealing with this. The constant rumbling and rough driving of the engine can create problems controlling the vehicle. If not that, your car could also experience complete engine failure if this is neglected long enough.

What repairs can fix the code?

repair manuals

Replacing faulty spark plugs is a good place to start when doing repairs. Damaged and/or faulty coils, valves and sensors should be replaced as well. If you noticed any kind of damage or other issues with your fuel injectors, those need to be replaced too.

It may also be necessary to replace the engine entirely if you notice any kind of cylinder damage. Before that, however, check for internal engine component damage and consider replacing any faulty parts.

Related codes

The related codes are quite simple to identify. The last issue just goes up one. So, P0302, P0303 and P0304 would all be similar codes to P0301.

Can I drive with a cylinder 1 misfire?

Any vehicle that has a misfiring cylinder can be irreparably damaged, so it is not advisable to drive. Cylinder misfires are typically caused by bad spark plugs or an imbalanced air/fuel mixture. You might be able to drive the vehicle a bit, but that is very unsafe as well.


Like we talked about, code P0301 should be handled quickly. No one wants to deal with long-term damage to their vehicle or have to deal with an unsafe car. If you see symptoms of a P0301 trouble code, run a diagnostics test immediately as well as a thorough visual inspection. This will help you identify the causes of the misfirings and let you get started on repairs right away.

P0301 Code – What Does It Mean & How To Fix It