P0300 on a 2019 Honda Pilot

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 2019 Honda Pilot

Ranked from 871 NHTSA owner complaints filed for this vehicle.

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1
Connecting rod bearing failure / engine knock (NHTSA recall 23V-751 investigation)
High severity
An overwhelming number of owners report a metallic rod-bearing knock progressing to catastrophic engine failure on the 3.5L V6; the resulting crank-speed irregularity and rough running is repeatedly logged alongside the check-engine light before the engine fails outright. This is a known Honda/Acura J35 bearing defect under NHTSA investigation.
Reported in 14 NHTSA complaints
2
Fuel injector or fuel rail assembly failure
Medium severity
Several owners report a failed fuel rail assembly or injector-related emissions fault (some tied to Honda's fuel injector recall/warranty extension) that produced check-engine lights, hesitation, and rough idling consistent with misfire.
Reported in 3 NHTSA complaints
Parts:fuel injector fuel rail assembly
3
Worn or fouled spark plugs
Low severity
Common wear item and the first thing to check on any random-misfire code; inspect gap and electrode condition, especially near the recommended replacement interval.
Common cause
Parts:spark plug
4
Failing ignition coil
Medium severity
A weak or cracked individual coil-on-plug unit drops spark energy to one cylinder, often worse when the engine is hot.
Common cause
Parts:ignition coil
5
Vacuum or intake leak
Medium severity
Unmetered air entering through a cracked hose or intake gasket leans out one or more cylinders enough to misfire, most noticeable at idle.
Common cause
6
Carbon-fouled intake valves
Low severity
Direct-injection V6 engines like this one are prone to carbon buildup on the intake valves since fuel never washes them, disrupting airflow and causing intermittent misfires.
Common cause
7
Low compression from worn rings, valves, or bearing-related cylinder damage
High severity
Mechanical wear or the internal engine damage seen in this dataset's rod-bearing failures reduces a cylinder's ability to seal and burn fuel cleanly.
Common cause

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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