P0305 Code – Meaning, Causes, Symptoms (& How To Fix)

If you have scanned your engine computer to see what’s causing trouble and found the P0305 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 P0305. You will learn what could happen and the best way to fix it. 

Definition of Code P0305

P0305 – Cylinder #5 Misfire Detected

What is the P0305 Coding?

P0305 DTC means that there’s an engine misfire in cylinder 5. Powertrain control module (PCM), which detects a misfiring engine in cylinder 5, alerts the engine and sets the trouble code. It’s a generic code, applying to all OBD-II equipped models.

Although the trouble code P0305 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 P0305 Symptoms

You should be able to notice performance problems if one engine cylinder is not firing. The Check Engine Light will also be on when you set the code, alerting to any problems. 

Here are some of the top symptoms you’ll notice with the P0305 DTC.

What causes the Code P0305?

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 P0305 trouble codes.

Is the P0305 Code Really Serious?

Extreme – The P0305 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 P0305 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 P0305?

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
• Replacing the coil/wires
• Replace your fuel injector
• Fix leaking valve
• Repair vacuum leak
• Replacing the piston ring
• Repair leaking head gasket
• Replacing computer module

Common mistakes in diagnosing P0305

Most often, misfires are caused by spark plugs. However, you should never assume that’s the problem without first performing the diagnostic steps we outline. It is important to inspect the wires, plugs, coils, as well as coil packs before you replace them. 

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 do you diagnose the P0305 trouble code?

Professional mechanics should follow a plan for diagnosing P0305 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.

These are some of the more common steps to diagnose the P0305 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. Check the spark plug and ignition coil as well as any coil packs on cylinder 5, 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. 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. Older cars may also require you to check the distributor cap or the ignition cables. 
8. A compression test on cylinder 5 is required. 
9. Inspect the camshaft timing, and the timing belt/shaft if needed.
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. 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 P0305 Code: Mechanics Tips

It is possible to replace the cylinder 5 plug, if the problem causes the p0305 error code. However, it’s always a better idea to replace all of the plugs at the same time. One plug is likely to fail, and the rest will soon 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. 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.

Other Trouble Codes

Commonly Asked Questions