P0300 on a 2022 Honda Civic Hatchback

P0300 is a generic OBD2 powertrain code for random or multiple cylinder misfire. Unlike P0301 through P0308, it does not point to one specific cylinder, so the cause can be ignition, fuel, air, sensor, or mechanical.

Not your vehicle? See general P0300 info.

Most common causes on the 2022 Honda Civic Hatchback

Ranked from 880 NHTSA owner complaints filed for this vehicle.

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1
Leaking fuel injector causing fuel wash-down and cylinder fouling
High severity
Honda's own service diagnosis on this vehicle found a leaking #2 fuel injector washing raw fuel into the cylinder, fouling/breaking spark plugs and ultimately destroying the head — a documented failure mode on this L15B7/L15CA engine family.
Reported in 1 NHTSA complaint
Parts:fuel injector spark plug
2
Manufacturing debris causing internal engine damage/low compression
High severity
This nearly-new vehicle's engine failed with rod-knock symptoms; the dealer found a metal piece inside the engine consistent with a manufacturing defect degrading compression and combustion.
Reported in 1 NHTSA complaint
3
Worn or fouled spark plugs
Medium severity
Aged or fuel-fouled plugs misfire under load; inspect and gap/replace per interval.
Common cause
Parts:spark plug
4
Failing ignition coil(s)
Medium severity
A weakening coil produces a weak spark that misfires under load or when hot; swap-test to a known-good cylinder to confirm.
Common cause
Parts:ignition coil
5
Vacuum or intake leak
Low severity
Unmetered air entering downstream of the throttle leans out a cylinder enough to misfire, especially at idle.
Common cause
6
Carbon buildup on intake valves
Low severity
Direct-injection engines like this one don't get fuel washing the intake valves, so carbon accumulates and can disrupt airflow/combustion in one or more cylinders over time.
Common cause
7
EGR valve fault
Low severity
A stuck-open EGR valve introduces excess exhaust gas at idle/low load and can cause a rough idle or misfire.
Common cause
Parts:EGR valve

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0300 on your car still needs shop confirmation before any repair.

Common symptoms

Flashing or steady check engine light
Rough idle
Shaking under acceleration
Loss of power
Fuel smell from exhaust

What to check before replacing parts

Scan for cylinder-specific misfire codes

Look for: A companion P0301–P0308 pins the misfire to one cylinder — start there. P0300 with no cylinder code points at something hitting several at once: fuel pressure, a large vacuum leak, or timing.

Inspect the spark plugs and coils

Look for: Pull the plugs: black/sooty = rich, oily = oil intrusion, white/blistered = lean or overheating, cracked porcelain or an out-of-spec gap = replace. Then swap a coil to another cylinder — if a cylinder-specific code follows the coil, the coil is bad.

Check fuel trims for a vacuum leak

Look for: High positive short- and long-term trims (worst at idle, improving as RPM rises) mean unmetered air is getting in. Smoke-test the intake and listen for hissing.

Verify fuel pressure

Look for: Compare running/cranking pressure to the vehicle spec. Low or dropping pressure starves multiple cylinders and reads as a random misfire — suspect the pump, filter, or regulator.

Compression / leak-down test if ignition and fuel check out

Look for: A cylinder 15%+ below the others, or leak-down hissing from the intake (intake valve), exhaust (exhaust valve), or oil filler (rings), means the misfire is mechanical — not a swap-in part.

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Matching symptoms

Car Runs Rough Flashing Check Engine Light