Loading P0301…
Read the code correctly
P0301 confirms that the engine computer detected a misfire assigned to Cylinder 1; it does not prove the coil, spark plug, injector, or a mechanical fault is the cause. Test or swap one accessible part at a time before buying replacements.
Approximate engine-bay orientation only: Cylinder 1 can sit in a different bank or fore-aft position depending on the engine layout. Use the vehicle-specific firing order and component diagram before removing parts.
Inspect here, in order
- 1
Cylinder 1 location
Approximate engine-bay anchor · position varies by layout
Find the cylinder labeled 1 in the vehicle-specific firing-order diagram; the physical position is not universal across inline, V, and boxer engines.
- 2
Ignition coil serving Cylinder 1
At the top of Cylinder 1 or connected by a plug wire
Inspect the coil body, electrical connector, and boot for oil, cracking, corrosion, or a loose connection before condemning it.
- 3
Spark plug beneath the coil / boot
Threaded into the Cylinder 1 head
With the engine cool, check the plug well and boot, then compare the plug condition and gap with the manufacturer specification.
- 4
Cylinder-1 fuel injector
Along the matching intake runner or fuel rail
Trace the fuel rail or intake runner to the same cylinder and inspect the injector connector, wiring, and signs of a restricted or leaking injector.
Platform caveat
Cylinder 1 position varies by inline, V, and boxer engine layout, as well as by make, model, year, and engine family. Confirm the vehicle-specific firing order and service diagram before unplugging an injector or reaching below the intake manifold.
Safe setup
Work on a cool engine, keep hands and clothing clear of belts and fans, disconnect ignition or fuel components only with the engine off, and leave fuel-pressure or compression testing to a properly equipped setup.
Public platform notes