P2308 Code: Ignition Coil “C” Secondary Circuit

A P2308 code might appear on your scan tool while you’re diagnosing your vehicle. There are many ways to resolve diagnostic trouble codes (DTCs) like this one, but you’ll need to figure out what triggered it in the first place so that you can perform the appropriate repairs. If you have any questions about code P2308 and how to troubleshoot it, we’ll try to answer them in this OBD-II article.

What Does the P2308 Code Mean?

A P2308 code is usually defined as “Ignition Coil ‘C’ Secondary Circuit.” This is a generic powertrain code that applies to select modern vehicles that have OBD-II.

Your vehicle’s powertrain control module (PCM) can store a P2308 if it detects an abnormal voltage condition in the ignition coil’s secondary circuit designated with the letter “C”. The exact location of ignition coil “C” can vary depending on the vehicle’s model, but it usually refers to the ignition coil at cylinder number three. A P2308 code is usually be accompanied by an illuminated malfunction indicator lamp.

On a modern vehicle, the ignition coil’s secondary circuit usually consists of the spark plug and secondary windings inside the coil-on-plug ignition coil. Meanwhile, the ignition coil’s primary circuit includes the primary windings inside of the coil-on-plug ignition coil, an engine RPM sensor (usually the crankshaft position sensor), the powertrain control module (PCM), and corresponding circuitry. The ignition switch supplies battery power to the primary circuit.

If the PCM detects a problem with the ignition coil “C” circuit, it will store code P2305 in memory.

You may also watch this video to understand how ignition coil works:

Note: The definition of code P2308 might be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P2308 Code?

The issues that set a P2308 code can be caused by a number of factors. Here are some of the most common causes.

• Faulty ignition coil
• Circuit issues, such as damaged wires and poor connections
• Worn-out spark plugs
• An issue with the PCM, such as software in need of an update

What are the Common Symptoms of the P2308 Code?

DTCs other than code P2308 can be registered in your vehicle’s PCM. This can cause confusion when diagnosing your system because some symptoms might not be listed here. However, if your PCM only has a P2308 stored, you can expect one or more of the following symptoms to manifest.

• Illuminated check engine light
• Misfiring
• Poor engine performance
• Reduced fuel efficiency

How to Diagnose the P2308 Code

Diagnosing a P2308 can be challenging due to the complexity of your vehicle’s electrical system. You might end up replacing the wrong component if you don’t know what you’re doing. The video below shows how you might go about diagnosing a P2308 code on certain vehicles, but you still have to consult your vehicle’s specific repair manual or repair database to figure out the right fix. If this sounds like a lot of work, you’re probably better off taking your vehicle to a mechanic for repairs.

How to Fix the P2308 Code

There’s no one way to resolve a P2308 code. You’ll have to find the underlying problem or problems triggering this code to figure out the right fix. This usually requires some experience and knowledge in auto repair. Some manufacturers publish technical service bulletins for recurring problems online, so you might want to browse the internet for OBD-II resources. Chilton’s repair manuals can be invaluable for DIYers. If you have some cash to spare, you can enroll in ALLDATA’s single-vehicle subscription to get detailed information on your specific vehicle.

You should never use a repair manual from another manufacturer because some terms might be different. Don’t hesitate to call your mechanic if you don’t feel confident in troubleshooting this DTC.