P0306 Code – Meaning, Causes, Symptoms (& How To Fix)

If you have scanned your engine computer to see what’s causing trouble and found the P0306 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 meaning of P0306's trouble code. This guide will also explain what could happen if this happens and how you can fix it. 

Definition of the code P0306

P0306 – Cylinder #6 Misfire Detected

What is the P0306 Codification?

P0306 DTC means that there’s an engine misfire in cylinder 6. Powertrain Control Modules (PCM) alert the engine when misfiring occurs in the sixth cylinder of the car's motor. It’s a generic code, applying to all OBD-II equipped models.

The P0306 trouble code can be taken as a generic one, but repairs will depend on what make and model of vehicle you have. 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. 

P0306 Trouble Code Symptoms

Performance issues can be noticed if an engine cylinder fails to fire. In addition, the Check Engine Light will turn on when you set the code, alerting to the issue. 

Here are some of the top symptoms you’ll notice with the P0306 DTC.

What causes the Code P0306?

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.

Below are the most frequent causes for the P0306 trouble code.

Is the P0306 Code Really Serious?

Very severe – The P0306 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 P0306 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 your vehicle breaks down. 

Which Repairs can Fix the Code P0306

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.

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
• Vacuum leakage fixed
• Change the piston ring
• Repair leaking head gasket
• Replace computer module

Common errors in P0306 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 do you diagnose the P0306 trouble code?

When diagnosing the code P0306, 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 P0306 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. Set the code back to default.
3. You can test drive your vehicle and see which codes return.
4. To determine if the coil pack, spark plug or ignition coil on cylinder 6 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, you will need to perform a compression test for cylinder 6. 
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 P0306 Code: Mechanics Tips

It is possible to replace the plug if the problem with the 6 cylinder spark plug causes the p0306 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. You can also replace the spark plugs quickly and easily to keep on top of the recommended maintenance. 

Also, ensure that spark plugs have a proper gap. 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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