P0300 on a 2013 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 2013 Hyundai Sonata

Ranked from 1,896 NHTSA owner complaints filed for this vehicle.

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1
Connecting Rod Bearing Failure / Engine Seizure (Theta II Defect)
High severity
A known defect in the Theta II GDI engine causes premature connecting rod bearing wear, leading to metallic knocking, metal shavings in oil, sudden loss of power, and engine seizure. This is heavily documented in the complaints and often triggers limp mode or stalling.
Reported in 14 NHTSA complaints
2
Excessive Oil Consumption
High severity
The engine burns oil at an abnormally high rate, leading to low oil levels without warning lights. This oil starvation can cause misfires, internal engine damage, and eventual engine failure.
Reported in 4 NHTSA complaints
3
Knock Sensor Detection System (KSDS) / Software Issues
Medium severity
The KSDS software update is designed to detect bearing wear and put the car into limp mode (often throwing code P1326). Complaints note the system triggering limp mode abruptly at highway speeds, sometimes requiring software updates to clear.
Reported in 4 NHTSA complaints
4
Faulty Spark Plugs
Low severity
Worn or fouled spark plugs fail to ignite the air-fuel mixture properly, leading to random or multiple cylinder misfires. This is a standard diagnostic check for P0300.
Common cause
5
Faulty Ignition Coils
Medium severity
Failing ignition coils cannot provide the necessary voltage to the spark plugs, causing misfires across multiple cylinders. This is a common generic cause for a P0300 code.
Common cause
6
Vacuum Leaks
Medium severity
Unmetered air entering the intake manifold leans out the air-fuel mixture, causing random misfires. Look for cracked hoses or a failing intake manifold gasket.
Common cause
7
Low Fuel Pressure / Failing Fuel Pump
Medium severity
Inadequate fuel delivery prevents proper combustion, leading to random misfires. This can be caused by a failing fuel pump, clogged fuel filter, or faulty fuel pressure regulator.
Common cause
8
Faulty Mass Air Flow (MAF) or Oxygen (O2) Sensors
Medium severity
Incorrect data from these sensors causes the engine computer to miscalculate the air-fuel ratio, resulting in a mixture that is too rich or too lean and causing random misfires.
Common cause

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