What Does the Engine Code P0301 Mean?

A P0301 engine code will display after your engine detects a misfire.
Written by Max Werner
Reviewed by Melanie Reiff
A P0301 code displays when your ECM (engine control module) detects a misfire from cylinder one of your engine. Misfire events can happen for many reasons and should be addressed immediately to prevent further damage to your vehicle.
Diagnostic trouble codes (DTCs) are invaluable for identifying engine trouble. An OBD-II code reader can tell you what a code means, but it cannot identify the source of a problem—so identifying the DTC is only half the battle when it comes to vehicle repairs.
To ensure you’re on the right track, the
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What does the engine code P0301 mean?

Definition: Cylinder 1 misfire detected
A P0301 code happens when a misfire is detected from the first cylinder of your engine
Engines create power through combustion reactions. Combustion takes place in the cylinders, but when this reaction fails, you’ll experience an
engine misfire
—an abrupt loss of RPMs when your engine fails to produce enough power.

How much will it cost to fix?

Most auto shops will charge from $75 to $150 to diagnose the problem. From there, repair or replacement costs will vary significantly based on the parts needed and the extent of the damage.

What can cause the P0301 engine code?

A P0301 engine code displays when your engine control module (ECM) detects a misfire in cylinder one. Misfires can happen for various reasons, but there are a few common causes.
Problems with the ignition system:
  • Faulty worn spark plug
  • Faulty coil pack or plug
  • Poor spark plug wiring
Issues with fuel delivery:
  • Poor fuel injector circuit wiring
  • Faulty powertrain control module
Other mechanical issues:
  • Leaking valve
  • Worn piston ring or damaged piston
  • Worn crankshaft lobe
  • Damaged filter
  • Leaking head gasket
Multiple cylinders may even misfire due to a single problem—meaning you won’t always need extensive repairs to fix multiple misfire-related codes.
MORE: Does insurance cover engine failure?

Common symptoms of the P0301 engine code

As soon as the P0301 code appears, your
check engine light will turn on
. Drivers can also expect the following symptoms:
  • Rough idling
  • Hard starting
  • Jerking motion while idle
  • Jerking motion while moving
  • Unusually sluggish acceleration
Generally, a car whose engine is misfiring will feel as though it has lost power—so you’ll notice the biggest issues during quick acceleration attempts. 

How serious is the P0301 engine code? 

A P0301 engine code should never be taken lightly. If left unchecked, cylindrical misfires can cause extensive damage to your engine. You should have the code inspected by a qualified mechanic as soon as possible.
Extreme cylindrical misfiring can also damage the catalytic converter—which will cause the malfunction indicator lamp (MIL) to flash. This component is integral for your engine to operate correctly and can be expensive to replace.

Can I fix the P0301 engine code myself?

Unless you have a mechanical background, you’ll likely be unable to fix this issue on your own. You can, however, inspect your engine to try to narrow down the cause of the issue.
When inspecting your engine cylinder, look for the following signs of damage:
  • Corroded electrical connections
  • Bent, broken, or out-of-place components
  • Fluids leaking from around the cylinder
You may be able to solve the misfire issue by
replacing the spark plugs
on the cylinder. If the problem persists after the new plugs are added, you should visit a mechanic.

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