P0301: Cylinder 1 Misfire Detected

What does P0301 mean?

The engine computer counted misfires on cylinder 1 only. On most engines cylinder 1 sits at the timing-belt/chain end of the engine (on V engines, the front of bank 1), but numbering varies by maker, so confirm the location in a service diagram before pulling parts. A single-cylinder code is good news diagnostically: it points to a part that serves only that cylinder.

Generic OBD-II definition: Cylinder 1 Misfire Detected. Confirm applicability in your vehicle service information.

Common causes

• Worn, cracked, or oil-fouled spark plug in cylinder 1
• Ignition coil or coil boot for cylinder 1 failing (boots often crack and arc to the cylinder head)
• Clogged or electrically failed cylinder 1 fuel injector
• Oil leaking into the plug well from a valve cover or tube seal
• Low compression in cylinder 1 from a burnt valve or worn rings

Symptoms

• Steady shake at idle that may smooth out at higher RPM
• Check engine light that flashes under load
• Smell of raw fuel from the exhaust in severe cases

Can I keep driving with P0301?

Severity: High Stop or minimize driving and get it looked at right away.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

• Confirm which physical cylinder is #1 for your engine
• Swap cylinder 1's ignition coil with a neighboring cylinder's coil, clear codes, and drive: if the code moves to that cylinder, the coil is bad
• If the coil isn't it, swap the plug to another cylinder the same way
• Look for oil pooled in the plug well, which points to a leaking seal
• If spark and fuel test good, run a compression test on cylinder 1 and compare to the others