P0300 on a 2017 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 2017 Honda Pilot
Ranked from 903 NHTSA owner complaints filed for this vehicle.
- 1
Connecting rod bearing wear/failure (known J35Y6 3.5L V6 issue)
High severityOverwhelming pattern in this batch: engine knocking, rod bearing pitting/spinning, and outright rod-through-block failure — a well-documented issue on 2016-2020 Honda Pilots with this V6 — which drops cylinder compression and produces misfire/knock codes; several complaints link it directly to cylinder misfire codes (e.g. P0301/P0304).
Reported in 11 NHTSA complaints - 2
Clogged or leaking fuel injector(s)
Medium severityFaulty fuel injectors were replaced alongside a rod-bearing/knock diagnosis on this vehicle, unbalancing cylinder fueling.
Reported in 1 NHTSA complaintParts:fuel injector - 3
Worn spark plugs
Low severitySpark plugs were replaced as a first-line fix for a reported cylinder misfire before the underlying rod-bearing issue was found.
Reported in 1 NHTSA complaintParts:spark plugs - 4
Failing ignition coil
Medium severityA weak or failed coil-on-plug unit drops spark energy to one cylinder, producing a misfire code isolated to that cylinder.
Common causeParts:ignition coil - 5
Vacuum/intake leak
Medium severityUnmetered air leaning a cylinder's mixture, typically worse at idle; check intake gaskets and PCV/vacuum hoses.
Common cause - 6
Carbon-fouled intake valves
Low severityDirect-injection V6 engines are prone to intake-valve carbon buildup disrupting airflow and combustion, contributing to misfire.
Common cause - 7
EGR valve fault
Low severityA stuck-open EGR valve over-dilutes the idle mixture, producing a misfire.
Common causeParts: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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