What does the P0301 code mean?

P0301 means the engine control unit has detected repeated misfires in cylinder 1, the first cylinder in the firing order. The ECU watches tiny crankshaft speed drops on each combustion event, and once cylinder 1 misses enough times within a set window it stores the code. Unlike P0300 (random misfire across several cylinders), P0301 isolates the fault to one cylinder, which makes diagnosis faster.

What are the symptoms of a P0301 misfire?

Common signs are a rough or shaking idle, a rhythmic stumble, vibration felt in the steering wheel or seat, hesitation and lost power on acceleration, higher fuel use, and sometimes a fuel or rotten-egg smell from the exhaust. The check engine light is on, and a flashing light means cylinder 1 is misfiring hard enough to risk the catalytic converter right now.

What causes a P0301 code?

The two most common causes are a worn cylinder-1 spark plug and a failed cylinder-1 ignition coil. After those come a clogged or leaking injector on cylinder 1, a vacuum leak at that intake runner, damaged plug wiring, and, less often, low compression from a burnt valve, worn rings, or a head gasket leak. Because the fault is on one cylinder, start with the cheap ignition parts before opening up the engine.

Is it safe to drive with a P0301 code?

It is not recommended. A persistent cylinder-1 misfire pushes raw fuel into the exhaust, which can overheat and ruin the catalytic converter, a far more expensive repair than a plug or coil. If the check engine light is flashing, pull over and stop driving. If it is steady and the engine still runs, drive only the short distance needed to reach a workshop.

How do you fix and clear a P0301 code?

Fix the root cause first, then clear the code. The fastest test is to swap the cylinder-1 coil with an adjacent cylinder, clear codes, and see if the misfire follows the coil. If it does, replace the coil; if not, fit a new spark plug, then check the injector, wiring, and compression. After the repair, an OBD2 scanner clears the stored code, but it will return if the underlying fault was not fixed.

How much does it cost to fix P0301, and where is cylinder 1?

A spark plug runs about 10-40 EUR and an ignition coil about 40-200 EUR, both quick jobs that are often DIY-friendly. Injector cleaning or replacement is roughly 100-380 EUR, while compression-related valve or head gasket repair can reach several hundred to over a thousand euros. Cylinder 1 is usually at the timing-belt or chain end on inline engines; on V-engines it sits on a specific bank, so check the firing-order label or owner's manual.

P0301: Cylinder 1 Misfire Detected

Quick Answer

Not safe to drive

P0301 means the engine computer has counted repeated misfires isolated to cylinder 1, the first cylinder in the firing order. Combustion in that cylinder is incomplete or absent, so the engine runs rough and loses power. The most common cause by far is a worn cylinder-1 spark plug or a failed ignition coil. A replacement plug costs only 10-40 EUR, so start there before chasing fuel or compression faults.

Severity: High · Misfire
Estimated repair cost: From €40 to €1700+, varies by vehicle

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What does P0301 mean?

P0301 is a misfire-related diagnostic trouble code classified as high severity. When your vehicle's ECU detects this condition, it stores P0301 and illuminates the check engine light.

What are the symptoms of P0301?

If your vehicle has triggered P0301, you may notice one or more of these symptoms:

Check engine light on steady, or flashing during a hard misfire
Rough idle with a rhythmic stumble or shake
Noticeable vibration felt through the steering wheel or seat
Reduced power and hesitation during acceleration
Increased fuel consumption from raw fuel passing through cylinder 1
Fuel or rotten-egg smell from the exhaust and occasional exhaust popping

What causes P0301?

Here are the most common causes of P0301:

Worn or fouled cylinder-1 spark plug, the eroded electrode or wide gap stops a reliable spark from igniting the mixture
: high
Failed cylinder-1 ignition coil, a breakdown in the coil windings or boot delivers a weak or intermittent spark to that cylinder only
: high
Clogged or leaking cylinder-1 fuel injector, a blocked nozzle or stuck injector starves or floods that cylinder so it cannot burn cleanly
: medium
Vacuum leak at the cylinder-1 intake runner or a cracked manifold gasket, extra unmetered air leans out just that cylinder
: medium
Low compression in cylinder 1 from a burnt or leaking valve, worn rings, or a failing head gasket, so the charge cannot build enough pressure to fire
: low
Damaged plug wire, connector, or coil harness on cylinder 1, corroded or open wiring interrupts the firing signal to that cylinder
: low

Is it safe to drive with P0301?

No - address this immediately. A single-cylinder misfire can quickly overheat and destroy the catalytic converter. Continued driving also risks engine damage from unburned fuel washing cylinder walls. Address this code as soon as possible.

How do you diagnose P0301?

Follow these steps to pinpoint the root cause of P0301:

Read freeze-frame data to capture RPM, engine load, and coolant temperature at the moment the misfire was logged, which narrows cold-start versus load-related faults
Swap the cylinder-1 ignition coil with the coil from cylinder 2, clear the code, and drive. If the misfire moves to cylinder 2 (now P0302), the coil is the fault
Remove and inspect the cylinder-1 spark plug for electrode wear, carbon fouling, oil, or an out-of-spec gap. Compare it side by side with a plug from a healthy cylinder
Confirm the cylinder-1 injector is clicking with a noid light or stethoscope, and check its resistance and wiring connector for an open or corroded pin
Run a compression test on cylinder 1 and compare to its neighbours. More than a 10 percent drop, or a low reading that rises after adding oil, points to rings or valves
Smoke-test or spray-test the cylinder-1 intake runner for a vacuum leak, and scan live fuel trims for a lean correction that tracks that cylinder

How much does P0301 cost to fix?

Repair costs for P0301 vary depending on the root cause and your vehicle. Here are typical estimates:

Repair	Parts Cost	Labor Cost	Total Estimate	DIY Difficulty
Replace spark plug (cylinder 1)	€10–€40	€30–€80	€40–€120	Easy
Replace ignition coil (cylinder 1)	€40–€200	€30–€100	€70–€300	Easy
Clean or replace fuel injector (cylinder 1)	€40–€180	€60–€200	€100–€380	Moderate
Head gasket or valve repair	€150–€500	€400–€1200	€550–€1700	Professional

Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.

Full repair guides

Engines known for this code

P0301 on specific vehicles

P0301 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

P0301 on BMW

BMW 3 Series

See BMW-specific causes & cost

P0301 on Volkswagen

Volkswagen Golf

See Volkswagen-specific causes & cost

P0301 on Audi

Audi A4

See Audi-specific causes & cost

P0301 on Ford

Ford Focus

See Ford-specific causes & cost

P0301 on Opel

Opel Astra

See Opel-specific causes & cost

P0301 on Skoda

Skoda Octavia

See Skoda-specific causes & cost

These codes are often seen alongside P0301 or indicate related issues:

Common questions about P0301

What does the P0301 code mean?: P0301 means the engine control unit has detected repeated misfires in cylinder 1, the first cylinder in the firing order. The ECU watches tiny crankshaft speed drops on each combustion event, and once cylinder 1 misses enough times within a set window it stores the code. Unlike P0300 (random misfire across several cylinders), P0301 isolates the fault to one cylinder, which makes diagnosis faster.
What are the symptoms of a P0301 misfire?: Common signs are a rough or shaking idle, a rhythmic stumble, vibration felt in the steering wheel or seat, hesitation and lost power on acceleration, higher fuel use, and sometimes a fuel or rotten-egg smell from the exhaust. The check engine light is on, and a flashing light means cylinder 1 is misfiring hard enough to risk the catalytic converter right now.
What causes a P0301 code?: The two most common causes are a worn cylinder-1 spark plug and a failed cylinder-1 ignition coil. After those come a clogged or leaking injector on cylinder 1, a vacuum leak at that intake runner, damaged plug wiring, and, less often, low compression from a burnt valve, worn rings, or a head gasket leak. Because the fault is on one cylinder, start with the cheap ignition parts before opening up the engine.
Is it safe to drive with a P0301 code?: It is not recommended. A persistent cylinder-1 misfire pushes raw fuel into the exhaust, which can overheat and ruin the catalytic converter, a far more expensive repair than a plug or coil. If the check engine light is flashing, pull over and stop driving. If it is steady and the engine still runs, drive only the short distance needed to reach a workshop.
How do you fix and clear a P0301 code?: Fix the root cause first, then clear the code. The fastest test is to swap the cylinder-1 coil with an adjacent cylinder, clear codes, and see if the misfire follows the coil. If it does, replace the coil; if not, fit a new spark plug, then check the injector, wiring, and compression. After the repair, an OBD2 scanner clears the stored code, but it will return if the underlying fault was not fixed.
How much does it cost to fix P0301, and where is cylinder 1?: A spark plug runs about 10-40 EUR and an ignition coil about 40-200 EUR, both quick jobs that are often DIY-friendly. Injector cleaning or replacement is roughly 100-380 EUR, while compression-related valve or head gasket repair can reach several hundred to over a thousand euros. Cylinder 1 is usually at the timing-belt or chain end on inline engines; on V-engines it sits on a specific bank, so check the firing-order label or owner's manual.

Read our detailed guides

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