What Codes Will This Page Cover?
The code definitions you’ll find on this page are:
- P0307 Cylinder 7 Misfire Detected
- P0308 Cylinder 8 Misfire Detected
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What Is the P0307 Code?
Symptoms
Causes
Seriousness
Can I Still Drive?
Diagnose
Difficulty of Inspecting
Get Additional Help
The definition of codes P0307 and P0308 are “Cylinder 7 Misfire Detected” and “Cylinder 8 Misfire Detected,” respectively. The definitions are also self-evident. They indicate that your powertrain control module (PCM) or engine control module (ECM) has detected a misfire condition in either Cylinder 7 or Cylinder 8, depending on the specific code. This generic code will show up in a variety of OBD-II-equipped vehicles but will only show up in a vehicle with eight cylinders.
You might also be interest in P0300 – Random/multiple Cylinder Misfire Detected
More About Error Code P0307
Each cylinder in your vehicle is part of the process that converts rotational motion to linear motion and back again, causing your vehicle to move forward. At the top of the cylinder is a spark plug, which is a device that uses a fuel/air mixture compressed inside the cylinder to fire a spark, which sets fire to the fuel. That fuel creates the energy necessary to power the crankshaft. The crankshaft RPM may change if the cylinders aren’t firing properly, as they won’t create a consistent amount of power. These codes indicate that the crankshaft position sensor signal shows an increase or decrease in crankshaft revolutions per minute of at least 2%.
What Are the Symptoms of a P0307 Code?
The common symptoms associated with the P0307 and P0308 codes will vary depending on the actual cause of the code. However, there are a few common symptoms. It may be difficult to start your vehicle, and in some cases, that may build to a complete no-start condition. The vehicle may also stall during acceleration or at stops, and rough running is often a problem in general. The vehicle may lack power while driving, and an increase in fuel consumption is also common. The check engine light should also turn on. If the increase or decrease in crankshaft RPM is more than 10%, your check engine light will probably start flashing, which indicates a severe problem that you should address immediately.
What Are Some Causes of a P0307 Code?
There are seemingly endless possible causes of the P0307 and P0308 codes because just about any issue related to the engine can end up creating a misfire condition, especially if it gets bad enough. Here are a few potential causes of these codes:
- Faulty fuel injectors
- Bad fuel pump
- Faulty spark plugs
- Issues with the spark plug wires
- Faulty ignition coil
- Vacuum leak, intake leak, or other air leak
- Faulty camshaft position sensors
- Faulty crankshaft position sensors
- Faulty MAF sensor
- Faulty oxygen sensors
- Faulty throttle position sensor
- Incorrect level of compression in cylinder
- Incorrect fuel pressure
- Fault in the wiring harness or connector pins
- Inaccurate ignition timing
- Excessive wear and tear
- Problems with the catalytic converter
- Faulty PCM
As you can see, the variety of possible causes can be overwhelming. This code should not be your starting point when it comes time to diagnose the problem.
How Serious Is the P0307 Code?
The P0307 and P0308 codes should be taken quite seriously. Even if the problem is just an issue with a bad cam sensor, there’s no way for you to effectively tell the core of the issue just by knowing that your vehicle is throwing one of these codes. Inaccurate ignition timing can throw off the entire vehicle and, in many cases, lead to serious engine damage. Treat these diagnostic trouble codes as extremely serious.
Can I Still Drive with a P0307 Code?
In some cases, it will be impossible for you to drive with these codes, as it may result in a no-start condition. However, regardless of the condition, you should not drive with the P0307 and P0308 codes active. These codes indicate a very significant concern with your ignition components, which are some of the most important components of your engine. Even if you’re experiencing a general lack of power, it’s best to play it safe.
How Easy Is It to Diagnose a P0307 Code?
If you couldn’t tell from the massive list of possible causes, diagnosing P0307 and P0308 codes can be extremely difficult. You shouldn’t usually use the P0307 and P0308 codes as your primary source of determining what the underlying problem is. Most of the time, there will be additional codes stored that will give you more information about where in the vehicle the problem is and how you can fix it. If you’re not confident in doing this, talk to a professional mechanic.
How Difficult Is It to Inspect a P0307 Code?
It can be quite difficult to inspect the P0307 and P0308 codes because of how much information you need. Of course, you need a code scanner to start with. You should also gather freeze frame data, technical service bulletins, vehicle service guides, and other reliable information sources. It’s important to have all the information necessary to inspect the P0307 and P0308 codes, so talk to an expert before you start doing it yourself.
Need Additional Help with Your P0307 Code?
It’s common to need extra help with the P0307 and P0308 codes. If you’re looking for solutions, a professional will be able to help.
Start by finding an auto repair shop in your area. A local auto repair shop will be especially important if you have a no-start condition, as this will allow you to discover a great repair without paying too much for a tow truck.
These codes are also not where you should start with your diagnostic process. The OBD-II database at KBB.com will give you insight into any other trouble codes you see on your code scanner.
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