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The diagnostic trouble code P0301 is defined as the “Cylinder 1 Misfire Detected” fault code.
It is a generic OBD-II trouble code triggered when your vehicle’s PCM (Powertrain Control Module) detects an engine misfire from your first cylinder.
When you have an active P0301 diagnostic trouble code, your vehicle’s Powertrain Control Module has detected a more than 2% increase or decrease in the camshaft’s revolutions per minute. This triggers your check engine light to come on.
If your check engine light is flashing on and off, the percentage increase or decrease in camshaft revolutions per minute is more than 10%.
In short, if you have a misfire in your engine cylinder 1, it reduces your crankshaft’s revolutions per minute, and your PCM will give you the P0301 diagnostic trouble code.
Every car engine has multiple cylinders, whether you own a Ford, Toyota, BMW, or Honda motor company vehicle. Cylinder number 1 in misfire code P0301 refers to the first cylinder in the firing order.
For example, V8 engines usually have cylinders numbered 1-4 on the passenger side and 5-8 on the driver’s side. V6s may have them labeled 1-3 on the front bank and 4-6 on the rear bank, depending on your engine design and manufacturer.
Note: The cylinders’ firing order doesn’t necessarily follow the numbering system, so make sure you know which cylinder is first in the firing order. You can consult your car owner’s manual or an online repair manual to find out.
However, P0301 only refers to an engine misfire problem in cylinder 1. Likewise, P0302 refers to a misfire problem in cylinder 2, P0303 to cylinder 3, and so on.
You may experience one or more of these common symptoms when your car has an active P0301 code:
If you have an active P0301 code, you should stop driving immediately.
An engine cylinder misfire can lead to an ignition system failure or engine stalling, which is incredibly dangerous.
Furthermore, driving with a misfiring engine could damage other parts of your car, like your catalytic converter. A catalytic converter replacement job is expensive, so fixing the fault code ASAP will save you time and money.
There are multiple possible causes for the P0301 code and a cylinder misfire, some more common than others.
These are the most common possible causes of a cylinder 1 misfire and code P0301:
Code P0301 and a misfiring engine are less frequently caused by:
Your mechanic will run a series of troubleshooting checks to determine what caused your P0301 code and how to fix the cylinder misfire.
Mechanics generally start troubleshooting the easiest and cheapest to fix problems before moving on to more complex repairs.
Here’s how your mechanic will diagnose and fix the misfire code:
Before your mechanic replaces your spark plug and spark plug wire or coil pack and coil pack wire, ask them to inspect your fuel injector wiring. Damaged fuel injector wiring could be causing the engine misfire in cylinder 1, and diagnosing this first could save time.
Sometimes, there are other overlooked issues including loose-fitting electrical connectors and disconnected vacuum hoses that can trigger code P0301.
Your mechanic will replace any car part or equipment that has caused the P0301 code, whether it is the spark plugs or spark plug wires, the ignition coil packs and connectors or the fuel injector.
The repair costs depend on the cause of the cylinder misfire.
Note: The repair costs mentioned above exclude labor charges.
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