P0308 Code – Meaning, Causes, Symptoms (& How To Fix)

If you have scanned your engine computer to see what’s causing trouble and found the P0308 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.

We will be discussing the meanings and possible causes of the trouble code P0308. You will learn what to do if it happens, and we also provide suggestions on how to fix it. 

Definition of Code P0308

P0308 – Cylinder #8 Misfire Detected

What is the meaning of P0308?

P0308 DTC means that there’s an engine misfire in cylinder 8. The Powertrain Control Module, or PCM, detects that the engine is misfiring in cylinder 8. This alerts the engine to change the trouble code. It’s a generic code, applying to all OBD-II equipped models.

Although the P0308 trouble code is generic in nature, repairs may be required depending on your make or model. Multiple misfires could result in the code P0308 being combined with related codes that indicate issues with other cylinders. 

Trouble Code P0308 Symptoms

Performance issues can be noticed if an engine cylinder fails to fire. As soon as the code has been set, you will see the Check Engine Light, which alerts you to the issue. 

Here are some of the top symptoms you’ll notice with the P0308 DTC.

The P0308 Code: Causes

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.

These are the top causes of P0308 trouble codes.

What is the P0308 code?

Extreme – The P0308 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. It can be dangerous to drive if your engine stops.

It’s important to have the P0308 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 P0308?

It is essential to perform an extensive diagnosis before you begin any repair. 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
• Vacuum leakage fixed
• Change the piston ring
• Repair leaking head gasket
• Replace computer module

Common mistakes in diagnosing P0308

The misfires are usually caused by spark plugs. 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. A compression test is also recommended. Additionally, if there are any other trouble codes present, these might help you narrow down what’s going on. 

How do you diagnose the P0308 trouble code?

Professional mechanics should follow a plan for diagnosing P0308 codes. 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.

These are some of the more common steps to diagnose the P0308 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. You can test drive your vehicle and see which codes return.
4. Check the spark plug and ignition coil as well as any coil packs on cylinder 8. If they are damaged or worn, replace them. 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. A compression test on cylinder 8 is required beyond this. 
9. Inspect the timing gear and camshaft, as well as the timing shaft.
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. 

Calculated Cost for Repair

Depending on what’s causing the problem, you are looking at a varying amount of repair costs. You will pay less to repair some problems 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 P0308 Code: Mechanics Tips

It is possible to replace the ignition coil plug in cylinder 8, if that causes the p0308 error code. 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. 

Also, ensure that spark plugs have a proper gap. An improper gap can lead to misfires. Use a spark plug gap tool to ensure the space matches the manufacturer’s specs.

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