Hyundai Check Engine Code
P0300 on Hyundai
Random / Multiple Cylinder Misfire Detected
Also covers: Kia, Genesis
P0300 on Hyundai: what makes it different
P0300 — random or multiple cylinder misfire detected — appears frequently on Hyundai vehicles across several engine families. The Theta II 2.4L and 2.0L GDI engines are particularly susceptible due to known carbon buildup on intake valves causing irregular combustion, while the older 2.7L Delta V6 used in the Santa Fe and Sonata has a documented history of ignition coil failures. The Nu 1.8L and Gamma 1.6L engines also see P0300 related to coil-on-plug failures and spark plug fouling.
Most-affected engines
- Theta II 2.4L GDI (Sonata, Santa Fe, Tucson)
- Theta II 2.0L GDI (Sonata, Elantra GT)
- Delta 2.7L V6 (Santa Fe, Sonata, Tiburon)
- Gamma 1.6L GDI (Elantra, Accent, Veloster)
Common model years: 2006–2021
Most likely cause on Hyundai
Failed or intermittently failing ignition coil(s) on the coil-on-plug setup, most commonly on the Theta II and Delta engine families.
Known Hyundai engine-family issues
The Theta II engine family has been the subject of significant owner and regulatory attention related to oil consumption and internal engine wear at higher mileage, both of which can eventually manifest as misfires. The Delta 2.7L V6 is known within the Hyundai community for coil-on-plug boots that crack and cause arcing, producing random misfires that are often intermittent and difficult to catch during a standard scan. The Theta II GDI engines also have a documented timing chain stretch issue that can affect cam timing enough to cause random misfires, typically appearing above 100,000 miles.
Hyundai-specific causes (most common first)
- Failing coil-on-plug ignition coils — the coil boots degrade and allow arcing, a recurring issue on the Theta II engine family
- Fouled or worn spark plugs, particularly on GDI engines where carbon deposits on intake valves also contribute to plug fouling
- Heavy intake valve carbon deposits on GDI engines causing inconsistent cylinder filling and combustion
- Contaminated or clogged GDI fuel injectors not delivering a consistent spray pattern
- Stretched timing chain on the Theta II engine affecting valve timing and causing cylinder-specific or random misfires at higher mileage
- Low compression in one or more cylinders on high-mileage Theta II engines, tied to the broader engine reliability concerns in that family
Hyundai-specific diagnostic tip
On Hyundai coil-on-plug engines, a practical first step is to swap coils between cylinders — for example, move the coil from cylinder 1 to cylinder 3 and clear the code. If the misfire follows the coil to cylinder 3, the coil is the culprit. If the misfire stays on cylinder 1, the problem is the plug, injector, or a mechanical issue. On Theta II GDI engines at higher mileage, also pull the spark plugs and inspect for oily or carbon-fouled electrodes, which point toward internal engine wear requiring further investigation before simply replacing ignition components.
Symptoms drivers report
- Check engine light (often flashing — flashing means catalytic damage is happening now)
- Rough idle, shuddering
- Loss of power
- Hesitation or stumble under load
- Smell of unburned fuel
Typical repair cost on Hyundai
Most Hyundai owners fix P0300 for between $60 and $1200, depending on which underlying cause turns out to be at fault. Start with the most-likely cause for your vehicle — Failed or intermittently failing ignition coil(s) on the coil-on-plug setup, most commonly on the Theta II and Delta engine families. — before throwing parts at it.
Hyundai P0300 FAQ
Why do Hyundai coil-on-plug ignition coils fail so often?
The coil boots — the rubber sleeves that seal the coil to the spark plug well — are exposed to significant heat cycles and tend to crack or harden over time. Once a boot cracks, the high-voltage spark can arc to the engine block instead of jumping the plug gap, causing a misfire. This is a known weakness across several Hyundai engine families and is one of the first things to check when P0300 appears.
Can the timing chain cause a random misfire (P0300) on my Hyundai Sonata or Santa Fe?
Yes, on the Theta II engine a stretched timing chain can retard camshaft timing enough to affect the combustion event in a way that produces random or rotating misfires, especially under load. If P0300 is accompanied by P0011 or P0013 (camshaft timing codes) or a rattling noise on cold start, have the timing chain stretch evaluated promptly.
Should I replace all spark plugs and coils at once if I have P0300 on a Hyundai?
If the vehicle has high mileage and the plugs and coils are original, replacing all plugs and coils as a set is often the most cost-effective approach. Individual ignition components on these engines tend to be near end-of-life at similar mileages, and doing one at a time can lead to multiple repeat visits. If the vehicle is lower mileage, use the coil-swap diagnostic technique first to identify the specific faulty component.
Related codes
Drive a different make? See the general P0300 guide for cross-vehicle causes and symptoms.
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Most common fix for P0300:
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