EngineLightCodes
Powertrain code

P0301 Cylinder 1 Misfire Detected

Severity
Stop soon
Typical repair cost
$30–$880
Do it yourself
Possible, easy
Shop time
0.3–4 hours

Cylinder 1 isn't burning its fuel properly, so the engine shakes or stumbles, most noticeably at idle or when you accelerate. Cylinder 1 sits at the front of the engine on most cars, and a worn spark plug, a failing ignition coil or a cracked coil boot on that cylinder is the usual cause.

How the engine computer detects it

The engine module detects misfire from crankshaft speed: a cylinder that does not fire gives no acceleration impulse. At a catalyst-damaging rate (CARB: at least 5 % per 200 revolutions) the warning light flashes; at an emissions-relevant rate (at least 1 % per 1,000 revolutions – GM about 2–5 %, Ford 0.9–1.5 %) it comes on after two trips. Ford and GM may shut off a misfiring cylinder's injector to protect the catalyst. P0301 means more than 90 % of the detected misfires fall on cylinder 1. Usual causes are the ignition coil or spark plug of that cylinder, its injector, or low compression; a quick test is to swap coil or plug with a neighbouring cylinder and see whether the misfire moves. Bulletins for four-cylinder engines name internal coil faults (Mazda) and plugs cracked during installation (FCA).

Written from public technical sources and not yet checked by a mechanic. How we write these pages

Symptoms

  • Check engine light on, flashing at a catalyst-damaging rate
  • Rough idle, jerking, vibration
  • Loss of power, hesitation
  • Smell of unburnt fuel, higher consumption

Common causes

  1. Ignition coil of cylinder 1 faulty (coil, connector, ground) Most likely
  2. Spark plug of cylinder 1 worn, sooted, cracked or wrongly gapped Most likely
  3. Injector of cylinder 1 clogged or leaking, or its control Possible
  4. Low compression on cylinder 1 (valve, rings, head gasket) or local false air Less likely
  5. Water or oil in the plug well Less likely

How to diagnose P0301

  1. Find cylinder 1. On inline engines it's usually the one nearest the drive belts; on V engines it's at the front of bank 1. The repair manual or a diagram on the intake confirms it.
  2. With the ignition off, pull the cylinder 1 coil and look at its rubber boot. Cracks, white tracking marks or oil on the boot let the spark leak to ground.
  3. Swap the cylinder 1 coil with a neighbor, clear the code and drive. If the misfire moves with the coil, replace the coil.
  4. Check the cylinder 1 spark plug for a worn electrode, cracks or oil fouling. If the plugs are due, replace the whole set.
  5. If coil and plug check out, have the cylinder 1 injector and its connector tested, then a compression test done.

Vehicles that report P0301 most

VehicleYearsReportsMedian miles
Ford Escape2013–20245682k
Ford Edge2007–20204467k
Honda Odyssey2003–201929110k
Ford Fusion2014–20192574k
Honda Accord2008–20241985k
Honda CR-V2000–20191794k
Honda Pilot2006–201910103k
Hyundai Elantra2013–20187—
Kia Sorento2014–20226—
Ford Mustang2016–20206—

Counts of owner complaints to the NHTSA that mention P0301 (346 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.

Reading the code

P
Powertrain
0
Generic (SAE) code
3
Ignition system or misfire
01
Specific fault

Questions drivers ask

Can I drive with code P0301?

If the check engine light is flashing, pull over as soon as it's safe and switch off: raw fuel is overheating the catalytic converter. If the light is steady, a gentle trip to a shop is usually fine, but skip highway runs and heavy loads until it's fixed.

Will my car pass an emissions inspection with P0301?

Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.

Will P0301 clear by itself?

The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.

Can I fix P0301 myself?

Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.

Often reported together

Codes that owners mention in the same NHTSA complaints as P0301. They can point to a shared cause, so it's worth checking them together.

This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.