How to Fix Code P0301: Causes & Solutions for Cylinder 1 Misfire

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obd scanner with code p0301 on the screen

Is your check engine light illuminated on your car dashboard? If you see a P0301 code, your engine is misfiring on cylinder 1. This can cause various problems, from low compression to a bad spark plug. But don’t fret! We will do our best to help you solve this.

This blog post will help you diagnose and fix a P0301 code. We will also discuss the causes and symptoms of this trouble code. Read on to learn more about this code and get your car running like new again!

What is Code P0301?

The P0301 code indicates that cylinder number 1 is having problems igniting. When a cylinder does not contain enough fuel to burn completely, it will cause the engine to misfire. So how does a misfire happen? 

When the spark plug fires, the air and fuel mixture inside the cylinder is compressed. If there is not enough fuel in the mixture, the spark will not be able to ignite it, the engine will misfire, and the code P0301 will be set.

When P0301 appears, it should be fixed immediately as long-term driving with engine misfires could cause consequential damage to your engine. 

Symptoms of Code P0301

If the P0301 shows on your scanner tool and you wonder what causes it, there are some signs that you may experience. If your car is experiencing these symptoms, it's crucial to have the trouble code diagnosed and repaired as soon as possible. 

  • Check engine light on
  • Rough running engine
  • Hesitation when accelerating
  • Lack of power
  • Misfire noise
  • Fuel smell from the exhaust

Causes of P0301

There can be various reasons why cylinder number one is not igniting. Some possibilities are:

  • Damaged spark plug or wires
  • Faulty coil pack
  • Incorrect valve timing
  • Dirty or clogged fuel injector
  • Low compression in cylinder
  • Worn out valve seals
  • Vacuum leak
  • Low fuel pressure
  • Defective camshaft sensor
  • Defective crankshaft sensor
  • Engine timing off
  • Leaking head gasket
  • Low engine compression
  • Poor quality fuel

How to diagnose Error Code P0301?

Diagnosing the P0301 code is more complex than other codes because of several potential causes. The best way to determine the reason is to use an automotive scan tool to read data from the engine's computer and check for any stored trouble codes. 

It is best to have your car checked by professionals as they have advanced tools and training that can help pinpoint the exact problem. If you decide to do it on your own, here are the steps you can follow:

Step-by-Step Guide

  1. The first step is to scan the car for trouble codes. You can do this with an OBDII code reader.
  2. Perform a road test and pay attention to how the car performs. This will help you determine if the misfire affects how the car drives.
  3. Look for faulty connections in the ignition coils and damaged wiring. These might produce inexplicable misfire situations. If required, tighten or connect the connections.
  4. Inspect the spark plugs and the spark plug wires and see if they're worn out or damaged. If so, replace them with new ones.
  5. Check the fuel injectors for dirt or carbon deposits. It might require cleaning to restore its proper function.
  6. After cleaning the injector, check the fuel pressure. It should be between 29 and 45 psi (207 and 310 kPa). If it's low, add more fuel to the tank.
  7. You should also check if you have enough gas in the tank. Running out of fuel can also cause misfires.
  8. You should also check the engine for vacuum leaks. 
  9. Check for worn-out camshaft lobes, a stretched timing chain, and other mechanical valve train elements that are not operating as they should cause a misfire, which necessitates an extensive examination.
  10. Inspect if the crankshaft tooth or camshaft sensor gear is faulty or ruptured as it can cause misfiring. Using an oscilloscope to inspect the signal to discover whether the CKP (crankshaft position sensor) or CMP (camshaft position sensor) is causing the issue.

If all these parts are in good condition, the problem is likely with the engine itself. In this case, you might need to take it to a mechanic for further diagnosis and repair.

How to Fix the Code P0301?

The code P0301 is quite challenging to diagnose and can be a frustrating experience. However, there are some possible fixes that you can try before taking it to a mechanic. But as we always advise you, please have it checked by a professional if you are not skilled in automobile repair. Here is the list of the possible fixes you can do:

  • Replace spark plugs and wires
  • Check for vacuum leaks
  • Clean or replace the MAF sensor
  • Reprogram the PCM
  • Replace the fuel injector
  • Repair engine damage
  • Replace the burned valves
  • Repair the vacuum leaks
  • Repair or replace the leaking head gaskets

In many cases, the cause of a P0301 code can be something as simple as a bad spark plug or wire. So, if you are mechanically inclined and have the proper tools, it might be worth your time to replace these components first. You can follow these steps in replacing the spark plug.

Step-by-Step Guide to Replacing the Spark Plug on Your Car

What you Need:

  • Spark plug (make sure to get a spark plug that fits your car)
  • Anti-seize lube and dielectric grease
  • Spark plug socket
  • Hand tools (ratchet, sockets, snd wrenches)

What to do:

  • Park your car on a flat, dry surface and make sure the engine is cool.
  • Clean the engine area of dirt and debris to prevent anything from falling into the engine cylinder during spark plug replacement. 
  • Disconnect the battery. Ensure the positive and negative terminals do not become crossed with a foreign object such as a hand ratchet and cause a dangerous short circuit.

Step-by-Step Guide to Removing the Spark Plug Wire

  • Remove any interference items. 
  • Avoid reusing the old gasket after removing the upper intake plenum (if your car requires it ). A new gasket is needed.
  • To avoid harming the rubber boot or ripping the wire terminal away from the plug wire end, you must be cautious. 
  • First, pull it out with needle-nose pliers or a similar tool to remove the spark plug. Then twist the boot back and forth to release the connection from the spark plug. Again, be cautious.
  • The metal terminal that joins the spark plug within the boot must be removed simultaneously to avoid harm. The boot puller tool is the best way to do this.

Step-by-Step Guide to Removing the Coil on Plug (COP) Ignition Module

  • Disconnect the electrical connector from the ignition coil. 
  • Remove the two bolts that hold the COP ignition module in place.
  • Remove two more bolts that hold in the coil pack. These must also be removed before the coil pack can come out. Be careful not to lose any small parts that may fall out when the coil pack is removed.
  • Be careful to avoid damaging the COP coils because it will cause the high voltage to leak (short) to the ground causing a misfire and possible damage to other ignition components.
  • Examine the COP boots for signs of engine oil or anti-freeze contamination. First, you should address the leaks to protect the new parts from harm, especially if severe.

Step-by-Step Guide to Removing the Old Spark Plug

  • Using a socket wrench, remove the spark plug.
  • Be careful not to drop it into the engine.
  • If the spark plug is difficult to remove, spray a light coating of penetrating oil onto the threads and wait a few minutes for it to soak in before attempting to loosen it again.

Step-by-Step Guide to Installing the New Spark Plug

  • Apply a thin coating of anti-seize to the new spark plug threads.
  • Thread the plug into the hole by hand until it bottoms out.
  • Avoid using excessive force, or you may damage the plug or lines in the head.
  • Using a socket wrench, tighten the plug to the specified torque.

Common Mistakes When Diagnosing the Code P0301

While diagnosing the possible causes of every issue is crucial, some people tend to jump to conclusions without confirming the root of the problem. This can cause them to spend unnecessary time and money on repairs that won't fix the issue. Some of these common mistakes are:

  • Replacing spark plugs and coils without confirming that they're the problem
  • Replacing the entire ignition system without verifying that it's the cause of the misfire
  • Running wires and cables all over the engine bay without properly inspecting or diagnosing the issue
  • Not completing a quick visual inspection
  • Assuming the problem is with a particular cylinder without checking all of them
  • Not verifying that the spark plugs and wires are in good condition
  • Not checking for vacuum leaks
  • Not inspecting the fuel injectors for clogging or damage

P0301 Code FAQs

1. Is the P0301 Code Serious?

When a misfire occurs, unburned gasoline enters the exhaust (one or more cylinders are not burning it properly) and is sent to the catalytic converter. Unfortunately, the catalytic converter is not designed to clean up the exhaust with unburned fuel, so it'll soon become unreliable. This is an expensive repair, so it is best to address the problem quickly.

2.  Can I drive with the P0301 code?

It's best not to drive the vehicle if you suspect there is a problem with the engine. Driving with a misfiring engine can cause further damage and even catastrophic failure.

3. Does P0301 clear itself?

A P0301 code will usually clear itself after the fault is corrected. However, if the problem persists, the code may stay stored in the computer's memory.

4. Can I use any spark plug for my car?

It is not recommended to use non-OEM spark plugs in your car. The wrong plug can damage the engine and may not be covered under warranty.

5. Can I repair the P0301 at home?

Yes, as long as you know what you are doing because any incorrect repairs could cause further damage to the engine.


The P0301 code is one of the most serious engine trouble codes. If you're seeing this code, it's important to take your car in for a diagnostic inspection as soon as possible. The problem may be a bad spark plug or low compression in most cases. However, you or your mechanic should rule out other potential causes just to be safe.

If you're comfortable doing your repairs, it's possible to fix the problem at home. Address all potential causes before replacing any parts. If you're not confident in your ability to repair your car, take it to a qualified mechanic. 

We hope this article was helpful and walked you through diagnosing and fixing your P0301 code. Thanks for reading!