P0300 on a 2022 Hyundai Tucson
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 2022 Hyundai Tucson
Ranked from 364 NHTSA owner complaints filed for this vehicle.
- 1
Leaking/failing high-pressure GDI fuel injector(s) (TSB 22-FL-002H / 23-FL-002H-1)
High severityAn overwhelming share of these complaints describe repeated fuel injector replacements, cylinder misfire codes (P0302/P0303), shaking, stalling, and even fuel dilution of the oil — all tied by owners and dealers to Hyundai's well-documented 2.5L GDI injector defect.
Reported in 22 NHTSA complaintsParts:fuel injector - 2
Rocker arm / valvetrain mechanical failure requiring engine replacement
High severityTwo owners had catastrophic internal engine failure (a failed rocker arm; a cylinder "not contributing" with scuffing found on inspection) that required full engine replacement — a mechanical defect distinct from the injector issue.
Reported in 2 NHTSA complaints - 3
EGR valve failure
Medium severityOne owner had two separate EGR valve failures, which can upset the air/fuel charge enough to cause a misfire.
Reported in 1 NHTSA complaintParts:EGR valve - 4
Worn spark plugs or failing ignition coil
Medium severityStandard ignition-side wear is a common contributor to random misfire even when injectors are healthy.
Common cause - 5
Vacuum or intake leak
Medium severityUnmetered air entering after the throttle body leans the mixture and can produce a rough, misfiring idle.
Common cause - 6
Carbon-fouled intake valves
Low severityDirect-injection engines are prone to carbon buildup on the intake valves (no fuel washing them), which disrupts airflow and combustion.
Common cause - 7
Low compression from worn piston rings or valves
High severityOrdinary mechanical wear reduces cylinder sealing and produces a chronic misfire.
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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