P0301 means your engine's computer has detected repeated misfires specifically in cylinder 1. Unlike P0300 which flags random misfires across multiple cylinders, this code points to a localised problem with that cylinder's spark plug, ignition coil, fuel injector, or compression, making targeted diagnosis more straightforward.
What does P0301 mean?
P0301 means your engine's computer has detected repeated misfires specifically in cylinder 1. Unlike P0300 which flags random misfires across multiple cylinders, this code points to a localised problem with that cylinder's spark plug, ignition coil, fuel injector, or compression, making targeted diagnosis more straightforward.
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 or flashing
Rough idle with a rhythmic stumble
Noticeable vibration felt through the steering wheel or seat
Reduced power during acceleration
Increased fuel consumption
Possible fuel smell from the exhaust
What causes P0301?
Here are the most common causes of P0301, ranked by how likely they are to be the culprit:
highWorn or fouled spark plug on cylinder 1
highFailed ignition coil on cylinder 1
mediumFaulty or clogged fuel injector on cylinder 1
mediumVacuum leak near cylinder 1 intake runner
lowLow compression on cylinder 1 (valve or head gasket issue)
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 check RPM, load, and coolant temperature at the time of the misfire
Swap the ignition coil from cylinder 1 with another cylinder and clear codes. If the misfire follows the coil, replace it
Remove and inspect the spark plug on cylinder 1 for wear, carbon fouling, or oil deposits. Replace if worn or gap is out of spec
Use a stethoscope or noid light to confirm the fuel injector on cylinder 1 is clicking and receiving signal
Perform a compression test on cylinder 1 and compare to adjacent cylinders. A difference greater than 10% indicates an internal engine issue
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)
€5–€25
€30–€80
€35–€105
Easy
Replace ignition coil (cylinder 1)
€25–€120
€30–€100
€55–€220
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.
P0301 on specific vehicles
P0301 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:
P0301 on Volkswagen Golf
Volkswagen Golf • 2005-2024
On EA888 2.0 TSI engines, carbon buildup on the intake valves of cylinder 1 is a common cause of P0301. Walnut blasting every 60,000-80,000 km is recommended for direct-injection models. The 1.4 TSI can also suffer ignition coil failures on cylinder 1.
Volkswagen GolfIgnition coil failure on 1.4 TSI models
P0301 repair cost for Volkswagen Golf
Estimated costs for Volkswagen Golf ownersadjusted higher than average due to Volkswagen-specific parts pricing
Repair
Parts Cost
Labor Cost
Total Estimate
DIY Difficulty
Replace spark plug (cylinder 1)
€6–€29
€35–€92
€40–€121
Easy
Replace ignition coil (cylinder 1)
€29–€138
€35–€115
€63–€253
Easy
Clean or replace fuel injector (cylinder 1)
€46–€207
€69–€230
€115–€437
Moderate
Head gasket or valve repair
€173–€575
€460–€1380
€633–€1955
Professional
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0301 on Ford Focus
Ford Focus • 2005-2022
The 1.0 EcoBoost engine is prone to coolant intrusion into cylinder 1 due to a known head gasket weakness (degas bottle hose issue). Ford extended warranties on some 2012-2018 models. The 1.6 TDCi can suffer injector seal leaks on cylinder 1 causing misfires.
What causes P0301 on a Ford Focus?
Ford FocusCoolant intrusion on 1.0 EcoBoost (head gasket/degas hose)
Ford FocusInjector seal leak on 1.6 TDCi
P0301 on BMW 3 Series
BMW 3 Series • 2006-2024
The N54 and N55 engines are notorious for ignition coil failures. Cylinder 1 is at the front of the engine and is most exposed to heat soak, leading to earlier coil failure. BMW recommends replacing all six coils and plugs at 80,000 km.
What causes P0301 on a BMW 3 Series?
BMW 3 SeriesIgnition coil failure due to heat soak on N54/N55
BMW 3 SeriesCarbon buildup on intake valves (N54 direct injection)
P0301 repair cost for BMW 3 Series
Estimated costs for BMW 3 Series ownersadjusted higher than average due to BMW-specific parts pricing
Repair
Parts Cost
Labor Cost
Total Estimate
DIY Difficulty
Replace spark plug (cylinder 1)
€7–€35
€42–€112
€49–€147
Easy
Replace ignition coil (cylinder 1)
€35–€168
€42–€140
€77–€308
Easy
Clean or replace fuel injector (cylinder 1)
€56–€252
€84–€280
€140–€532
Moderate
Head gasket or valve repair
€210–€700
€560–€1680
€770–€2380
Professional
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0301 on Renault Megane
Renault Megane • 2006-2024
The 1.2 TCe (H5Ft) engine has a known issue with piston ring failure on cylinder 1 causing oil consumption and misfires. Renault extended the warranty to 100,000 km on affected 2013-2017 models. The 1.5 dCi can develop injector problems triggering P0301.
What causes P0301 on a Renault Megane?
Renault MeganePiston ring failure on 1.2 TCe causing oil burning in cylinder 1
Renault MeganeInjector failure on 1.5 dCi
Related diagnostic codes
These codes are often seen alongside P0301 or indicate related issues:
P0301 means your engine control unit has detected that cylinder 1 is not firing correctly. Each combustion event in that cylinder is monitored via crankshaft speed variations, and when enough misfires are counted, the code is stored.
Can a bad spark plug cause P0301?
Yes. A worn, fouled, or incorrectly gapped spark plug is the single most common cause of a single-cylinder misfire code. Replacing the spark plug on cylinder 1 is the first and cheapest step to try.
How do I find cylinder 1 on my engine?
Cylinder numbering varies by manufacturer. On most inline-4 engines, cylinder 1 is at the timing belt or chain end. On V-engines, check your owner's manual as it may be on either bank. The firing order label on the engine cover can also help.
Can I drive with a P0301 code?
It is not recommended. Continued misfires send unburned fuel into the catalytic converter, which can overheat and fail. If the check engine light is flashing, stop driving immediately to prevent expensive converter damage.
Why does P0301 appear alongside P0300?
P0300 logs when misfires are detected across multiple cylinders. If cylinder 1 misfires frequently enough, P0301 is also set. Fix cylinder 1 first, clear codes, and see if P0300 returns. It may have been triggered by cylinder 1 alone.
