P0301 Code: Cylinder 1 Misfire Detected

What does P0301 mean?

P0301 is one of the cylinder codes P0301 to P0312, and the last digit names the cylinder: P0301 means the engine or powertrain control module detected a misfire in cylinder 1 ^[1]. The computer finds misfires by watching crankshaft speed. A cylinder that does not fire fails to push the crankshaft, which slows for an instant, and the crankshaft position sensor reports the dip ^[2].

California's OBD II regulation requires the system to identify the specific cylinder that is misfiring whenever it can ^[3]. A cylinder code like P0301 is good news in one way: it tells you exactly where to start looking. If you also have P0300, the random misfire code, the problem may be spreading or may involve something cylinders share.

Where is cylinder 1?

Most automakers number cylinders from front to back, so on an inline engine cylinder 1 is at the front, the end with the timing belt or chain. V engines and flat (boxer) engines vary by maker, and Ford V8s put cylinder 1 at the front of the driver's side ^[1]. On a V engine, the bank that holds cylinder 1 is called Bank 1. Confirm the layout in your owner's manual or a repair guide for your engine before you touch anything.

What symptoms come with P0301?

The check engine light is often the first sign, but most drivers also feel something. FIXD lists the typical symptoms as a rough idle, lower fuel economy, and stalling or hesitation, plus a fuel smell, black smoke or overheating depending on the cause ^[1].

• Rough or shaky idle. One cylinder not pulling its weight makes the engine shake most at a stop, when nothing else smooths it out.
• Hesitation when you accelerate. Some misfires appear only under load, so the stumble shows up when you press the pedal.
• Fuel smell or dark smoke. Fuel that does not burn in cylinder 1 leaves through the exhaust.
• A light that comes and goes. Some misfires only happen cold, wet or under load, so the code may set and then go quiet for a while.

None of these symptoms tells you the cause by itself. They do tell you when to note conditions, such as whether the shake happens cold or warm, which helps the diagnosis below.

Is it safe to drive with P0301?

No. P0301 is a stop driving code. FIXD's answer is to avoid driving with it, because the misfire can damage the engine and catalytic converter and can cause stalling or power loss ^[1].

If the check engine light is flashing or the engine shakes badly, pull over where it is safe, turn the engine off and have the car towed. A flashing light is not random. California's OBD II rule requires it to blink once per second while the engine is misfiring at a level that can damage the catalytic converter ^[3]. The unburned fuel from cylinder 1 burns in the exhaust instead. Ford's 2007 F-550 owner guide warns that the resulting exhaust heat can damage the converter and other parts, possibly causing a fire ^[4]. Our flashing check engine light guide explains the warning in full.

With a steady light and a smooth engine, limit driving to a short, gentle trip to get it checked. No towing, no long highway runs.

What causes P0301?

Because only one cylinder is involved, the parts that serve cylinder 1 alone come first. FIXD lists the spark plug, plug wire or ignition coil, the fuel injector, a vacuum leak, sensors, the head gasket and the catalytic converter among the possible causes ^[1].

Cause	How it affects cylinder 1	What points to it
Worn or fouled spark plug	Weak or no spark	Worn electrode, carbon or oil on the plug
Failing ignition coil or plug wire	Spark too weak under load	Misfire moves when you swap coils
Clogged or dead fuel injector	Too little fuel in that cylinder	Coil and plug check out; no regular clicking
Vacuum leak near cylinder 1	Extra air leans out that cylinder	Hissing near the intake, worse at idle
Low compression	Burnt valve, worn rings or head gasket	Low reading on a compression test
Oil in the cylinder	Oil fouls the plug	Wet, oily plug on cylinder 1

Start with the cheap parts that serve only cylinder 1: the plug, the coil and its connector. Problems that affect every cylinder, such as low fuel pressure, usually set P0300 or several cylinder codes instead. A rough idle is often the first thing drivers notice; see what causes a rough idle.

How do you diagnose P0301?

Work from the free checks toward the tests that need tools. Keep the code stored until you have written down the freeze frame, because clearing it erases that record ^[2].

1. Scan and save. Record all codes and the freeze frame data (engine speed, load and temperature when it set). The OBD2 scanner guide shows how.
2. Look first. With the engine off and cool, check the cylinder 1 coil connector, the plug wire if there is one, and nearby vacuum hoses.
3. Check the plug. Remove the cylinder 1 spark plug and look for carbon or oil buildup or a worn electrode ^[1].
4. Swap the coil. Move the cylinder 1 coil to a cylinder that is not misfiring, clear the codes and drive. If the misfire moves with the coil, you have found the problem ^{[1] [2]}.
5. Hand off the rest. If the misfire stays on cylinder 1, the injector, fuel pressure and compression are next. Have a qualified technician check those, especially on direct injection engines, which run very high fuel pressure.

How do you fix P0301, and what does it cost?

Replace whatever the tests point to: the spark plug, the coil, a plug wire, a cracked vacuum hose, the injector, or engine parts if compression is low. Many owners replace all spark plugs as a set when one is worn, since they have the same mileage. We found no current, reliable price range for November 2026, so here is what drives the cost instead:

• The part. A spark plug or coil is a small job compared with an injector or valve work.
• Access. On some engines the cylinder 1 plug and coil are easy to reach; on others, parts must come off first, which adds labor.
• Damage from driving on it. A long misfire can harm the catalytic converter, which can later set P0420 and turns a small repair into a large one.

After the repair, clear the code and drive normally. Clearing a code does not fix anything. The check engine light can also go out on its own after three drive cycles in similar conditions without the misfire ^[3]. For inspection, a car with the light on will not pass a California Smog Check, and the readiness monitors need normal driving to complete ^[5].

Which vehicles get P0301 most often?

We found no public data that ranks vehicles by P0301. Bulletins show how a single cylinder can be singled out, though. A General Motors bulletin for 2008 to 2009 Chevrolet Silverado Hybrid and Tahoe Hybrid trucks with the 6.0L engine describes oil deposits on the number 1 spark plug that can cause a cylinder 1 misfire and set P0300 or P0301, traced to a worn number 1 cam bearing ^[6]. For a wider GM bulletin about misfires, see P0300 on Chevrolet, and use the code lookup tool for any other codes you find.