P0307 Code – Meaning, Causes, Symptoms (& How To Fix)

If you have scanned your engine computer to see what’s causing trouble and found the P0307 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 P0307. You will learn what to do if it happens, and we also provide suggestions on how to fix it. 

Definition of Code P0307

P0307 – Cylinder #7 Misfire Detected

What is the P0307 Codification?

P0307 DTC means that there’s an engine misfire in cylinder 7. Powertrain control module (PCM) alerts engine when misfiring occurs in 7 cylinders. It’s a generic code, applying to all OBD-II equipped models.

Although the trouble code P0307 might seem generic, repairs may be required depending on your make or model. You might also notice the P0300 code if there are several misfires. This could be combined with any other codes that indicate problems with other parts of your vehicle. 

Trouble Code P0307 Symptoms

Performance issues can be noticed if an engine cylinder fails to fire. You will be notified by the Check Engine Light if the code is entered. 

Here are some of the top symptoms you’ll notice with the P0307 DTC.

What causes the Code P0307?

A variety of issues can cause a car to stop working. In some cases, the issues could stem from the ignition system, but it’s also possible that something has failed with the fuel system.

Below are some common reasons for the P0307 trouble code.

Is the P0307 code serious?

Extreme – The P0307 DTC is considered one that should be taken seriously. An engine misfire could make driving dangerous. This is especially true if your car stalls in the middle. You could be in danger if the engine suddenly stops.

It’s important to have the P0307 trouble code examined as soon as possible. Other engine problems can be caused by misfiring engines, which will increase the cost of repairs. You might also need to hire a tow truck if your car is unable to start. 

How can you fix the code P0307?

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.

Here are some possible solutions based on the most common failures.

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

Common errors in P0307 diagnosis

Most often, misfires are caused by spark plugs, coil packs, coil coils, wires, or 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. 

You can then move on to parts that are not working properly. 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 P0307 Trouble Code

Professional mechanics should follow a plan for diagnosing P0307 codes. Gathering the code from the scanner is just the first step of figuring out what’s wrong. You will be able to find the solution by following the correct steps.

Below are the main diagnostic steps of the P0307 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. Check the spark plug and ignition coil on cylinder 7, as well as any coil packs, to determine whether they are damaged or worn. 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. Vacuum leaks can be found in the intake.
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 7. 
9. Inspect the camshaft timing, and the timing belt/shaft if needed.
10. If you can't find anything else with diagnostics, it is possible that the PCM needs to 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. Here are some of the most popular repairs, along with the average labor and parts costs.

• 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 P0307 Code: Mechanics Tips

You can replace the spark plug in cylinder 7, if you discover that it is causing the code p0307. 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. You can also replace the spark plugs quickly and easily to keep on the recommended maintenance schedule. 

It is also important to ensure the spark plugs have adequate gaps. 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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