P0300 on 2021-2024 Genesis GV80: Random Misfire Causes and Fixes

What's Unique About the 2021-2024 Genesis GV80

For the Genesis GV80 with the 2.5L T-GDI engine, the P0300 code is uniquely tied to a known software problem acknowledged by the manufacturer. Genesis issued a Technical Service Bulletin (TSB 25-01-051G) and an associated Service Campaign (914G) specifically to address random misfires (P0300) and cylinder-specific misfires (P0301-P0304) that occur during a cold start. The official remedy is an ECM software update to revise the misfire detection logic, making a trip to the dealership a crucial first step, unlike many other vehicles where P0300 would immediately point to part replacement.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on (solid or flashing)
• Rough or unstable idle, especially on a cold start
• Engine hesitation or stumbling during acceleration
• Noticeable shaking or shuddering from the engine
• Reduced engine power and poor acceleration
• Difficulty starting the engine
• Decreased fuel economy
• A "schedule service" warning may appear on the dash and you may receive an email notification

Most Likely Causes

1. Engine Control Module (ECM) Software Update Needed 🔴 High Probability Genesis has issued a specific service campaign (914G) and TSB (25-01-051G) for 2021-2024 GV80 models with the 2.5L T-GDI engine that experience misfires (P0300-P0304) during cold starts. This was prompted by the California Air Resources Board (CARB) determining the issue could cause excess emissions.
   How to confirm: A Genesis dealership can check your vehicle's VIN against their system to see if Service Campaign 914G is open for your vehicle. Owners on forums report the dealer performs this automatically during service visits.
   Typical fix: The dealership will update the ECM software with improved misfire logic at no cost to the owner. The process is reported to take less than an hour.
   Est. part cost: $0
2. Worn or Fouled Spark Plugs 🟡 Medium Probability Spark plugs are a standard wear item on all gasoline engines. High-output turbocharged direct-injection (T-GDI) engines can be demanding on ignition components, leading to wear.
   How to confirm: Remove the spark plugs and inspect them for wear (worn electrode), damage, or deposits (carbon, oil, etc.). The gap should also be checked against manufacturer specifications. A worn plug is a very common cause of misfires.
   Typical fix: Replace all four spark plugs as a set. It is recommended to use OEM-spec plugs, which are often made by NGK for Hyundai/Genesis.
   Est. part cost: $80-$150
3. Faulty Ignition Coils 🟡 Medium Probability Ignition coils can fail over time due to heat and vibration. While no widespread recall exists for coils on this engine, they are a common cause of misfires on modern vehicles.
   How to confirm: A common DIY method is to swap the ignition coil from a misfiring cylinder (if a specific cylinder code like P0301 is also present) 🎬 See how a technician diagnoses a specific cylinder misfire. with a coil from a known good cylinder. Clear the codes, run the engine, and see if the misfire code follows the coil to the new cylinder.
   Typical fix: Replace the faulty ignition coil. 🎬 Watch: Step-by-step guide to replacing a GV80 ignition coil. Many technicians recommend replacing them as a set if they are original and have high mileage.
   Est. part cost: $70-$120 per coil
4. Leaking or Clogged Fuel Injectors ⚪ Low Probability The Theta III engine uses both GDI (direct) and MPI (port) injectors. While the port injection helps wash carbon from intake valves, the high-pressure GDI injectors can still become clogged or fail. Owners of platform mates like the Sonata N-Line have reported injector issues causing persistent misfires.
   How to confirm: This is more difficult to diagnose and may require a professional. It involves checking fuel trims with a scan tool and potentially performing a fuel injector balance test. A strong smell of fuel in the oil is a critical sign of a leaking injector.
   Typical fix: Clean or replace the faulty fuel injector(s). Replacement is often done in sets for balanced performance.
   Est. part cost: $150-$300 per injector

Rare But Worth Checking

• Low-Pressure Fuel Pump Failure: There is a recall (NHTSA 23V630000) for a failing low-pressure fuel pump on 2022-2023 GV80 models that can cause a sudden loss of power and may trigger misfire codes. A dealer can check if your VIN is affected.
• Internal Engine Mechanical Issues: In very rare cases, especially if symptoms like heavy oil consumption, blue/gray exhaust smoke, or knocking noises are present, a P0300 code could indicate a more serious internal problem like piston ring failure leading to low compression. This would require a compression and leak-down test to confirm.
• Carbon Buildup on Intake Valves: Although the 2.5T engine has a dual injection system (GDI and MPI) to help prevent carbon buildup, it can still occur over time on GDI-only engines. Significant buildup can restrict airflow into the cylinders, leading to misfires. This is less likely on this specific engine but a possibility on higher-mileage vehicles.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner and note any other codes present besides P0300. Freeze frame data 🎬 Watch: A helpful overview of diagnosing random P0300 misfires. can help identify conditions when the misfire occurred (e.g., cold start).
2. If you own a 2.5L T-GDI model, contact a Genesis dealership with your VIN. Ask if Service Campaign 914G regarding the ECM update for misfires is open for your vehicle. This should be your first step, as it's a free and highly probable fix.
3. If the ECM update has been performed or does not apply, inspect the ignition system. Remove and examine the spark plugs for signs of wear, fouling, or incorrect gap. The OEM part number is 18875-09085.
4. Inspect the ignition coils for any visible damage. If a specific cylinder misfire code (e.g., P0302) is present, swap that coil with one from another cylinder, clear the codes, and see if the misfire code moves to the new cylinder.
5. Check for vacuum leaks by inspecting all hoses connected to the intake manifold for cracks or loose connections. A vacuum leak introduces unmetered air and can cause a lean condition and misfires.
6. If the above steps do not resolve the issue, more advanced diagnostics are needed. This includes checking fuel pressure, testing fuel injectors, and performing an engine compression test to rule out mechanical issues.

Parts You'll Likely Need

• ECM Software Update — This is the official manufacturer fix for cold-start random misfires on the 2.5L T-GDI engine, as per TSB 25-01-051G and Service Campaign 914G.
  Trusted brands: Genesis
  OEM price range: $0
  Aftermarket price range: $0
• Spark Plugs (OEM #18875-09085) — Spark plugs are a common maintenance item and a frequent cause of misfires if worn or fouled.
  Trusted brands: Hyundai/Kia OEM (NGK), NGK
  OEM price range: $120-$180
  Aftermarket price range: $80-$150
• Ignition Coil (OEM #27300-2T000) — A failing ignition coil cannot provide enough energy to create a strong spark, leading to misfires.
  Trusted brands: Hyundai/Kia OEM, Bosch, Delphi
  OEM price range: $100-$150
  Aftermarket price range: $70-$120

Related Codes That Often Appear With This One

• P0301, P0302, P0303, P0304 — These are cylinder-specific misfire codes. P0300 often appears alongside one or more of these, indicating that while the misfires are random, the ECM has also identified which specific cylinders are most affected.

Technical Service Bulletins (TSBs) & Recalls

• 25-01-051G / Service Campaign 914G: Addresses P0300-P0304 misfire DTCs on 2.5L T-GDI engines at cold start via an ECM software update.

Platform-Specific Known Issues

• A Technical Service Bulletin (TSB 25-01-051G) was issued for 2021-2024 GV80s with the 2.5L T-GDI engine that may illuminate the check engine light with misfire codes P0300-P0304 during a cold start. The fix is a dealer-installed ECM software update.
• The California Air Resources Board (CARB) determined that this misfire issue could cause affected vehicles to release air pollutants exceeding state and federal standards, prompting the associated Service Campaign 914G.
• A recall (NHTSA ID: 23V630000) was issued for some 2022-2023 models for a failing low-pressure fuel pump that could cause a loss of power, which may present with misfire-like symptoms.
• Another unrelated OTA update was issued for some 2023-2024 GV80 models to address engine vibration during a hot idle, which could be confused with a misfire

Mechanic-Grade Diagnostic Values

• Fuel System Type — expected: Dual Injection: Gasoline Direct Injection (GDI) and Multi-Port Injection (MPI).. Failure: Diagnosis must account for both high-pressure and low-pressure fuel systems. A P0087 code (Fuel Rail Pressure Too Low) would point towards the GDI high-pressure side.

Hidden / Shadow Codes Worth Checking

• Cylinder-Specific Misfire Counts: While a basic scanner may only show a generic P0300, the Genesis GDS tool can display live data showing the exact number of misfire events per cylinder. This allows a technician to identify a cylinder that is misfiring frequently, even if it hasn't yet triggered a specific code like P0301 or P0302. (see via Genesis Diagnostic System (GDS) or an advanced professional scan tool with live data monitoring capabilities.)

Scan Tool Commands That Help

• Genesis Diagnostic System (GDS): Active Tests / Actuation Tests — After identifying a problematic cylinder via misfire counts, a technician can use the GDS to individually turn off the fuel injector or ignition coil for that cylinder. If the engine's running condition does not change when a component is deactivated, it confirms that component was not contributing, pointing to it as the source of the fault.
• Genesis Diagnostic System (GDS): Guided Diagnostics — The GDS software contains the official manufacturer troubleshooting procedures. For a P0300, it will provide a step-by-step diagnostic tree, prompting the technician to check specific values and components in the correct order, starting with the most common causes like the ECM update.

Wiring & Ground Locations

• Engine Compartment Fuse Box / Junction Block — Located in the engine bay, this panel houses fuses and relays critical to engine operation, including those for the ignition system, fuel pump, and ECM.. This is a central point for power distribution and contains multiple grounding points. A loose connection or corrosion in this area can cause intermittent power issues to the ignition or fuel systems, leading to random misfires.
• Passenger Compartment Fuse Box — Located inside the vehicle, typically behind the driver's side dash panel bolster.. This panel powers the ECM and various sensors. A fault here can lead to erratic ECM behavior and incorrect sensor readings, which could falsely trigger a P0300 code.
• Main Engine Grounds — While specific locations require a diagram, key grounds are typically found bolted from the engine block/cylinder head to the vehicle's chassis/frame.. The ignition coils rely on a solid ground connection to function. A loose or corroded engine ground strap can create high resistance in the ignition circuit, weakening spark and causing random, hard-to-diagnose misfires across all cylinders.

OEM Part Supersession History

• 27300-2T000 → 27300-2T000 — No supersession noted.
  Heads up: This ignition coil part number appears to be stable and is used across a wide variety of Hyundai, Kia, and Genesis models with the 2.5L Turbo engine from 2020 through 2026.

Model Year Variations Within This Range

• 2021-2024: The primary variation is the ECM software. TSB 25-01-051G was issued to correct misfire logic on these model years. It is likely that vehicles produced later in the 2023-2024 range may have received the updated software from the factory, while earlier 2021-2023 models would require the update to be performed by a dealer.