P0300 on a 2020 Honda Cr V
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 2020 Honda Cr V
Ranked from 335 NHTSA owner complaints filed for this vehicle.
- 1
Coolant intrusion into a cylinder from a failing head gasket
High severitySeveral owners had a dealer-diagnosed blown head gasket with coolant entering a cylinder; coolant in the combustion chamber fouls that cylinder and sets a misfire code.
Reported in 4 NHTSA complaints - 2
Cylinder misfire from oil dilution (fuel leaking into engine oil)
High severityThis 1.5T engine has a well-documented, class-action-referenced oil dilution issue (fuel mixing into the crankcase, especially from short/cold trips), which several owners in this batch confirmed via oil changes smelling of gasoline; diluted oil degrades lubrication and combustion consistency, contributing to misfire and flashing-CEL 'limp mode' events (an NHTSA investigation, PE25016, covers this pattern).
Reported in 3 NHTSA complaints - 3
Failing/leaking fuel injector(s)
High severityMultiple owners in this batch had a dealer-confirmed faulty fuel injector cause sudden misfiring, rough running, and loss of power, in some cases with a visible fuel leak/fire risk.
Reported in 2 NHTSA complaintsParts:fuel injector - 4
Turbocharger failure/oil intrusion
High severityMultiple owners had a dealer-diagnosed failed turbocharger accompanying sudden power loss and warning-light events; a failing turbo can dump oil into the intake or run boost erratically, disrupting combustion enough to trigger misfire/limp-mode codes.
Reported in 2 NHTSA complaintsParts:turbocharger - 5
Worn spark plugs
Low severityAged or oil-fouled plugs (worsened by this engine's oil-dilution tendency) misfire under load; inspect gap and fouling.
Common causeParts:spark plugs - 6
Vacuum/intake leak
Medium severityUnmetered air past the MAF leans a cylinder enough to misfire; smoke-test the intake tract.
Common cause - 7
Low compression (worn rings/valves)
High severityInternal wear reduces cylinder sealing; a compression or leak-down test isolates the affected cylinder.
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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