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  • Diagnostic trouble code (DTC) P0308 stands for “Cylinder 8 Misfire Detected.” This means the powertrain control module (PCM) detects that there was incomplete combustion or the absence of combustion in the cylinder numbered “8” in the arrangement of cylinders on the engine.
  • Common causes of the P0308 code include a bad spark plug, a faulty spark plug wire, and a failed ignition coil.
  • The symptoms that often accompany the P0308 code include an illuminated or flashing check engine light, the engine being hard to start or running rough, and the engine shaking.

An engine needs three elements to run: compression, spark, and a precise air/fuel mixture. When an engine cylinder misfires, the root cause originates from an issue with one of these three factors.

Driving your vehicle despite one or more of the cylinders misfiring may damage the engine. The P0308 code indicates that the powertrain control module (PCM) has detected a misfire on cylinder #8.

What are the repercussions of this trouble code, and what can you do to remedy the problem? Read this short guide to find out more.

What Does the P0308 Code Mean?

Diagnostic trouble code (DTC) P0308 stands for “Cylinder 8 Misfire Detected.” It indicates that the PCM perceives a misfire on cylinder #8.

Cylinder number 8 would refer, not to the eighth cylinder in the firing order, but the cylinder numbered “8” in the arrangement of cylinders on the engine.

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A misfire is caused either by incomplete combustion (or the absence of combustion) in one cylinder. Combustion is a small explosion that takes place when a pressurized air-fuel mixture is ignited inside the combustion chamber above each piston, and these explosions are timed very precisely for optimum power and efficiency.

Cylinder number 8 would refer, not to the eighth cylinder in the firing order, but the cylinder numbered “8” in the arrangement of cylinders on the engine.

– Richard McCuistian, ASE Certified Master Automobile Technician
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The P0308 code indicates that the powertrain control module (PCM) has detected a misfire on cylinder #8.

The combustion event superheats the inert nitrogen (which is 78% of the air charge) and the superheated nitrogen expands to drive the piston downward, which, applies torque by way of the connecting rods to the crankshaft, creating the rotational force delivered to the transmission or transaxle, which applies torque to the drive wheels. When a cylinder misfires, the crankshaft slows just a bit because the cylinder’s combustion event either didn’t take place or was weak.

The P0308 is associated with other engine misfire codes, specifically codes P0300 to P0312.

If you need more information to locate cylinder #8, read our explanation about cylinder location and firing order. Make sure you completely understand how cylinder misfires are identified by the PCM before attempting any DIY diagnosis or fix for code P0308.

What are the Possible Causes of the P0308 Code?

As mentioned above, misfires can trace their origin to a variety of factors. In the case of the P0308 code, these are the most common causes:

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Note: If additional misfire codes are stored, the list of potential causes may differ.

What are the Common Symptoms of the P0308 Code?

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An illuminated check engine light is one of the common symptoms associated with code P0308.

Listed below are just some common symptoms of the P0308 code. Note that you may encounter a combination of the signs below. Once you notice any of these issues, it’s a good practice to immediately check if the P0308 code or any other misfire code has been set. This is to avoid further damage to your engine and other parts of your vehicle.

How to Diagnose the P0308 Code

Diagnosing OBD-II codes may seem intimidating because you need to pinpoint their exact cause before attempting any repairs. And with the engine code P0308, there are quite a few causes.

If you’re a seasoned DIYer, there are a lot of repair guides and tutorials available online and in print to help you diagnose the code properly. Below are two online video resources that you can use to understand P0308 code and other misfire-related problems better:

How to Fix the P0308 Code

Figuring out a P0308 code fix is challenging, but it is possible. The key to determining the chief cause and an appropriate repair plan is to arm yourself with knowledge about how your vehicle works. Then, read up on what the error code is about.

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Note that there is no single fix for each OBD-II code and that repair steps will vary depending on the vehicle’s make and model.

Good thing there are repair manuals and guides with helpful illustrations available in the market, such as ALLDATA. Getting a subscription for repair guides is great, especially if you’re a dedicated DIYer. However, if you’re unsure about making a diagnosis and repairing your vehicle on your own, you can always have your mechanic do the job for you.

Other Notes About P0308

The P0308 is an OBD-II code with a high repair importance level. This means that it must be addressed right away. Ignoring this code might lead to one or more of the following scenarios:

  • Catalytic converter damage
  • Internal engine failure
  • Dangerous conditions while operating the vehicle

If you encounter this code, you must stop driving the vehicle and bring it to a shop for repairs immediately. The engine code P0308 has a high repair difficulty level and it might be best to let your mechanic deal with the issue, especially if you’re not confident in your skills as a DIYer.

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About The Authors
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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