P0301 Code – Meaning, Causes, Symptoms (& How To Fix)

If you have scanned your engine computer to see what’s causing trouble and found the P0301 code, you might wonder what is going on and how to fix it. Thankfully, it doesn’t take a lot of troubleshooting to get to the bottom of this issue.

This guide will explain the meanings and how to fix the trouble code P0301. This guide will also explain what to do if this happens and how you can fix it. 

Definition of the code P0301

P0301 – Cylinder #1 Misfire Detected

What is the P0301 Code?

P0301 DTC means that there’s an engine misfire in cylinder 1. Powertrain Control Modules (PCMs) alert the engine when a misfire is detected in the first cylinder of the car's motor. It’s a generic code, applying to all OBD-II equipped models.

The P0301 trouble code can be taken as a generic one, but repairs will depend on what make and model of vehicle you have. Multiple misfires could result in the code P0300 being displayed along with related codes to indicate issues with other cylinders. 

Trouble code P0301 Symptoms

You should be able to notice performance problems if one engine cylinder is not firing. The Check Engine Light will turn on in the event that the code has been set. This alerts you to the issue. 

Here are some of the top symptoms you’ll notice with the P0301 DTC.

The P0301 Code: Causes

There are many reasons why your car's engine may be stalling. In some cases, the issues could stem from the ignition system, but it’s also possible that something has failed with the fuel system.

These are the top causes of P0301 trouble codes.

What is the P0301 code?

Extreme – The P0301 DTC is considered one that should be taken seriously. A misfired engine can make it dangerous to drive, particularly if it causes the vehicle to stop in the middle. You could be in danger if the engine suddenly stops.

It’s important to have the P0301 trouble code examined as soon as possible. Other engine problems can be caused by misfiring engines, which will increase the cost of repairs. A tow truck may be required if the engine is not working properly. 

How can you fix the code P0301?

Before you make any repairs, it is important to do a thorough diagnosis. Otherwise, you could spend unnecessary money on parts that aren’t needed.

These are the solutions that we have found to be most effective based upon what is failing most frequently.

• Replace spark plug
• Replacing the coil/wires
• Install a brand new fuel injector
• Fix leaking valve
• Repair vacuum leak
• Replacing the piston ring
• Repair leaking head gasket
• Replace computer module

Common Mistakes in P0301 Diagnosis

The most common cause of misfires is the coil pack, spark plugs, coils, wires and ignition coils. However, you should never assume that’s the problem without first performing the diagnostic steps we outline. Before replacing the coil, you should first inspect all wires and plugs. 

These parts should look good. If they don't, then you can move to the parts that might be the problem, like the fuel injectors and valves. Also, you should perform a compression test. Additionally, if there are any other trouble codes present, these might help you narrow down what’s going on. 

How to diagnose P0301 Trouble code

When diagnosing the code P0301, a professional mechanic will want to use a structured plan. Gathering the code from the scanner is just the first step of figuring out what’s wrong. The right steps will give you the answer.

Below are the main diagnostic steps of the P0301 DTC.

1. Collect the trouble codes with your OBD-II scanner and use freeze frame data to see what’s going on. You can continue troubleshooting using the additional trouble codes that you find.
2. You can reset the codes.
3. To find out which codes are back, test drive the car.
4. To determine if the coil pack, spark plug or wire on cylinder 1 is worn or damaged, inspect it. Replace if necessary. You can try to move over the spark plug and ignition coil to another cylinder to see if you get a trouble code on the other cylinder instead – if so replace the faulty spark plugs and ignition coil.
5. For a vacuum leak, check the intake system.
6. If this isn’t the problem or the code doesn’t go away, you will need to inspect the fuel injectors. 
7. You might need to inspect the distributor cap as well as the ignition cables if you own an older vehicle. 
8. Above this point, it will be necessary to perform a compression test for cylinder 1. 
9. If necessary, check the timing of the camshaft and examine the shaft or timing belt.
10. If the diagnostics show no other problems, the PCM might be bad and should be replaced. However, with this problem, you’ll likely see other false codes or problems. 

The estimated cost of repair

Depending on what’s causing the problem, you are looking at a varying amount of repair costs. Repairs to some issues will cost less than others. We have listed below the top repairs as well as the average price for labor.

• Replace spark plug – $40-$350
• Replace ignition coils/wires – $75-$400
• Install a new fuel injector – $200-$500
• Fix leaking valve – $500-$2,500
• Replace piston ring – $1,000-$5,000
• Repair leaking head gasket – $1,500-$3,000
• Replace computer module – $750-$3,500

The P0301 Code: Mechanics Tips

You can replace the spark plug in cylinder 1, if you discover that it is the cause of the code p0301. However, it’s always a better idea to replace all of the plugs at the same time. The first one will fail and then the other ones will likely follow. It is easy to stick to a maintenance plan if you replace all the spark plugs at once. 

It is also important to ensure the spark plugs are properly gapped. It is possible to have a misfire if the gap between spark plugs and metal is not right. Use a spark plug gap tool to ensure the space matches the manufacturer’s specs.

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