P0300 on a 2016 Hyundai Sonata

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 2016 Hyundai Sonata

Ranked from 716 NHTSA owner complaints filed for this vehicle.

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1
Rod bearing wear with active knock-sensor detection code P1326 (Theta II engine defect / class-action settlement engine)
High severity
Multiple owners report the Knock Sensor Detection System flagging P1326 for rod bearing wear, entering limp mode, consistent with the well-documented Theta II rod bearing settlement on this generation of engine.
Reported in 4 NHTSA complaints
2
Oil-fouled spark plugs from chronic oil consumption (Theta II engine defect)
High severity
Owners describe repeated limp-mode/misfire episodes traced to spark plugs saturated with oil, requiring repeated plug (and sometimes coil) replacement without the underlying oil-consumption defect ever being fixed.
Reported in 3 NHTSA complaints
Parts:spark plugs valve cover gasket
3
Low compression / worn piston rings and cylinder walls from excessive oil consumption
High severity
One owner measured only 30 psi in a misfiring cylinder tied to a quart-per-500-mile oil burn rate, and others found metal particulate in the oil or a cylinder 'swimming' in oil, indicating internal wear severe enough to misfire.
Reported in 3 NHTSA complaints
4
Carbon/oil debris fouling the VVT sensor screen with multiple-cylinder misfire codes
Medium severity
One owner's independent shop found active P0301-P0305 misfire codes together with excessive debris on the VVT sensor screen and heavy oil consumption.
Reported in 1 NHTSA complaint
Parts:variable valve timing sensor
5
Failing ignition coil
Medium severity
Coil breakdown reduces spark energy to a cylinder; one owner's repeated misfire episodes included an ignition coil replacement alongside fouled plugs.
Reported in 1 NHTSA complaint
Parts:ignition coil
6
Vacuum leak
Medium severity
Unmetered air entering after the MAF disrupts the air/fuel ratio enough to cause a misfire, especially at idle.
Common cause
7
Clogged or leaking fuel injector
Medium severity
An injector delivering too little or an uneven spray pattern starves a cylinder of fuel and produces a steady misfire on that cylinder.
Common cause
Parts:fuel injector

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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