P0301 Engine Fault Code – Symptoms, Causes, Fix

Engine fault codes are also known as diagnostic trouble codes or DTC for short. Running into these codes is simply part of driving and owning a vehicle. Among the most common is engine fault code P0301. Many engines run into this issue, so what does this fault code mean? In this article, we discussing the meaning, symptoms, causes, and common fixes for the P0301 code.

DTC P0301 Meaning

P0301 – Cylinder 1 misfire detected.

This fault code is exactly as the description sounds. P0301 code simply means cylinder #1 is misfiring. Misfires occur when the cylinder does not achieve full combustion. The three primary things for an engine to run include air, fuel, and ignition. When the air-fuel mix is incorrect or ignition is weak or non-existent then the engine will misfire.

Fortunately, DTC P0301 is usually a pretty minor issue that is easy to repair. That’s especially true if this is the only diagnostic trouble code present. It’s not uncommon to see fault code P0300 present alongside P0301, though. This code means multiple cylinders are misfiring, so refer to the previously linked article if you’re experiencing multiple cylinder misfires.

Common Codes With P0301

P0300, P0302, P0303, P0304, P0305, P0306, P0307, and P0308

Again, you may experience multiple cylinder misfires. If this is the case you should receive misfire codes for the other cylinder(s) misfiring. P0301 simply refers to cylinder 1 while P0302 refers to cylinder 2. The list continues with the final digit indicating the misfiring cylinder.

P0301 Code Symptoms

Symptoms of engine fault code P0301 include:

• Check engine light
• Check engine light flashing
• Rough idle
• Stuttering / hesitation while accelerating
• Loss of power
• Poor engine performance

The specific symptoms of DTC P0301 can vary depending on the severity of misfires. It’s possible the misfires are happening consistently, or it may simply be every few minutes. Either way, a misfire from cylinder 1 should trigger the check engine light to turn on or flash. Sometimes the check engine light and P0301 code are the only symptoms.

With more severe misfires you will probably notice quite a few additional symptoms. These can include rough idle, hesitation during acceleration, loss of power, and poor overall performance from the engine. Note – power loss is not very common on larger engines (V6, V8, V10, etc) that only have cylinder 1 misfiring. It’s more common to notice with fewer cylinders since each one is making a larger percentage of total power output.

Is DTC P0301 Serious?

Severity Rating: Low

P0301 cylinder 1 misfire detected is typically a very low severity problem. This holds true when it is the only fault code present. Issues may be more severe if there are other codes indicating multiple cylinder misfires or other codes.

Anyways, you still want to diagnose the underlying problem and fix things as soon as possible. However, it’s unlikely code P0301 is going to cause any major drivability or long-term reliability concerns. When it’s the only code present you should be OK to continue driving. Use your own judgement, though. If certain other codes are present or something feels seriously wrong then it’s best to pull over in a safe location.

Engine Code P0301 Causes

Among the most common causes of DTC P0301 are:

• Spark plug
• Ignition coil / distributor
• Fuel injector
• Ignition coil wires

Misfires on cylinder 1 alone are almost always an issue with a part very specific to cylinder #1. Each cylinder has its own spark plug, ignition coil or distributor, and fuel injector. As such, these issues are by far the most common cause of code P0301.

Spark plugs and ignition coils are standard maintenance items. They’re wear and tear parts. Many cars need new spark plugs every 50,000 to 120,000 miles. However, it’s not uncommon for turbo engines to wear through spark plugs much sooner. Ignition coils typically last 100,000 to 200,000 miles. The same concept applies to turbo engines, though.

Fuel injectors or ignition coil wires are less common causes of DTC P0301. However, they’re still possible culprits and next up in line if the spark plug or ignition coil is not to blame.

Less Common Causes

There are a lot of problems that can cause misfires on an engine. Although, if P0301 cylinder 1 misfire is the only code present then these causes are pretty rare. It’s more common to see these causes with other codes present or multiple cylinder misfires:

• Fuel delivery issues (non fuel injectors)
• Vacuum leak
• Cam or crank sensors
• Poor fuel quality
• Incorrect ignition timing
• Loss of compression or other internal issues

Most of the above causes would affect multiple cylinders. For example, a fuel pump is responsible for delivering fuel to all or at least multiple cylinders. Cam or crank sensors affect the entire bank (ex: Cylinders 1-3 on an inline-6 engine). The same can be said for bad fuel quality or bad ignition timing. It’s possible for these problems to only trigger P0301 cylinder 1 misfires, but chances are it will trigger other codes and several misfires.

Lastly, loss of compression or other internal engine problems can cause code P0301. Problems of this severity are rare, but they do happen. Especially as engines age and near the end of their useful lives.

Diagnosing Fault P0301

Our focus here is diagnosing P0301 fault code when it’s the only code present. Refer to the article about P0300 multiple cylinder misfires detected if you have other codes present. Anyways, below are the steps to diagnose the underlying problems causing DTC P0301:

1. Confirm P0301 is the only engine fault code present.
2. Delete engine code with scanner and test drive. If the code does not come back then repeat this process. Keep an eye on things for the next few trips to see if code P0301 returns. If the code does return it’s time to diagnose the problem.
3. Visually inspect cylinder #1 ignition coil wiring. If nothing seems out of place then move on to the next step
4. This step is a multi-step process. The ignition coil lies on top of the spark plug, so it’s generally the best starting point to swap. Use the following method to diagnose the issues:
   1. Swap the ignition coil from cylinder #1 with another cylinder that is NOT misfiring
   2. Delete code and test drive. If the misfire follows the ignition coil to the new cylinder then you’ve found the culprit
   3. If the misfire remains on cylinder 1 then it’s not the ignition coil. Swap the cylinder 1 spark plug with another cylinder NOT misfiring
   4. Again, delete P0301 code and test drive to see if the misfire follows

Chances are the spark plug or ignition coil is the issue. If the misfire stays on cylinder 1 then it’s a bit more complex to continue diagnostics. Swapping fuel injectors is a lot more challenging. We typically don’t recommend swapping injectors unless you really know what you’re doing.

P0301 Code Fixes & Repairs

The specific repair, of course, depends on what you uncover during diagnostics. Most will find a faulty spark plug or ignition coil is the issue. If you were able to swap the plugs and coils successfully then you know how to handle replacements. It’s usually an easy job that even novice DIY’ers can knock out in the driveway in an hour or two.

Anyways, if your spark plug or ignition coil is at fault for P0301 then it’s usually a good idea to replace them on all cylinders. These are wear and tear parts. If one goes bad then the others will probably follow soon behind. They’re usually pretty inexpensive parts, so replacing all plugs or coils at once can save time and/or labor repair bills.

Diagnostic Code P0301 Repair Cost

Once you’ve located your underlying problem from DTC P0301 how much will it cost to repair? Below is a breakdown of common repair costs for the issues:

• Spark plugs: $25-300
• Ignition coils: $75-500
• Fuel injector: $50-300 (for 1 injector replacement)

Don’t worry about the higher end of the above quotes for repairs. Replacing all spark plugs on most engines will run about $25-100 in parts. However, some V8 engines, for example, use 2 spark plugs per cylinder. This can make replacing them more expensive. Some cars are harder to access spark plugs, which can drive up labor costs if you go to a repair shop.

Ignition coils will generally cost about $75-250 for a full set to replace them on all cylinders. Meanwhile, a single fuel injector can be even cheaper than $50. Some modern direct injection engines use much more expensive injectors, though.

DTC P0301 FAQ

To finish up this article we’re simply listing a few common question regarding P0301 code. Please note – some of this info was covered in the bulk of the article above.

What Does Code P0301 Mean?

P0301 refers to a cylinder #1 misfire. If this is the only code present it’s normally a simple problem. Refer to fault code P0300 if you’re experiencing misfires on multiple cylinders.

How Expensive Are Repairs?

Costs can vary a lot. However, if you’re only getting code P0301 then problems are usually inexpensive to repair. The cylinder 1 spark plug or ignition coil is usually to blame. It’s a good idea to replace all spark plugs or ignition coils at the same time. A set of spark plugs is generally about $25-100 while ignition coils are $75-200+.

Is It Safe To Drive With P0301 Present?

Yes – assuming P0301 is the only fault code present – it’s usually safe to continue driving the vehicle. This code is rarely a risk to drivability, longevity, or long-term reliability. It may be a different story if you’re receiving other engine fault codes, though.

What Is The Cause of the Code?

A faulty spark plug or ignition coil is the most common cause of cylinder #1 misfires. Start with these parts when diagnosing issues, but don’t overlook the basics like ignition coil wires.