P0302 on 2021-2024 Genesis GV80: Cylinder 2 Misfire Causes and Fixes

What's Unique About the 2021-2024 Genesis GV80

For the Genesis GV80 with the 2.5L Turbo engine, a P0302 code has a well-documented cause that is not a typical part failure. Manufacturer Technical Service Bulletins (TSBs) confirm that the original engine software can incorrectly detect misfires during a cold start. In these specific cases, the fix is a simple software update performed by a dealer, not a replacement of ignition parts. The 3.5L V6 does not have this specific software issue, and diagnosis would follow a more traditional path, with owner experiences pointing towards ignition coils and, 🎬 Watch a technician diagnose a persistent V6 engine misfire. less frequently, fuel injectors as potential culprits.

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 or flashing
• Rough or vibrating idle, especially on cold start
• Engine hesitation or stumbling during acceleration
• Reduced engine power and sluggish performance
• Smell of raw fuel from the exhaust
• Decrease in fuel economy

Most Likely Causes

1. ECM Software Update Needed (2.5L Engine Only) 🔴 High Probability Per TSB 25-01-051G, the original ECM software on some 2.5L T-GDI engines is overly sensitive and can log misfire codes P0300-P0304 during cold starts when no mechanical fault exists.
   How to confirm: Contact a Genesis dealership with your Vehicle Identification Number (VIN) and ask if Service Campaign 914G or TSB 25-01-051G is open for your vehicle. A user on the Genesis GV70 subreddit with the same 2.5L engine confirmed this exact TSB was the cause of their P0302 code.
   Typical fix: A Genesis dealer performs an Engine Control Module (ECM) software update, which improves the misfire detection logic.
   Est. part cost: $0 (if under warranty/campaign)
2. Faulty Ignition Coil 🟡 Medium Probability → Shop Ignition Coil Coil-on-plug systems are a common failure point on most modern engines. A technician with a 3.5T GV80 documented an intermittent P0302 that was resolved by swapping the coil to another cylinder and confirming the misfire code followed it 🎬 Watch: Helpful DIY tips for diagnosing a Hyundai or Genesis misfire. to the new cylinder (P0304).
   How to confirm: Swap the ignition coil from cylinder 2 with another cylinder (e.g., cylinder 4 on the 3.5T, or cylinder 1/3 on the 2.5T). Clear the codes and drive the vehicle. If the code changes to P0304, P0301, or P0303, the coil is faulty.
   Typical fix: Replace the failed ignition coil. 🎬 See this walkthrough on how to replace the ignition coil. It is often recommended to replace the corresponding spark plug at the same time.
   Est. part cost: $95-$155
3. Worn or Fouled Spark Plug 🟡 Medium Probability → Shop Spark Plug
   How to confirm: Remove the spark plug from cylinder 2. Inspect it for wear on the electrode, carbon buildup, or oil/fuel fouling. The service interval for spark plugs is typically around 48,000 miles, though some schedules suggest replacement later.
   Typical fix: Replace the spark plug. It is best practice to replace all spark plugs as a set to ensure even performance.
   Est. part cost: $25-$40 per plug
4. Leaking or Clogged Fuel Injector ⚪ Low Probability → Shop Fuel Injector Gasoline Direct Injection (GDI) engines, like those in the GV80, can be susceptible to carbon buildup on injector tips. Forum discussions for the related GV70 with both 2.5T and 3.5T engines show owners having misfire codes resolved by replacing all fuel injectors under warranty, indicating it's a known issue.
   How to confirm: This requires advanced diagnostics, such as an injector balance test or waveform analysis. A strong smell of fuel in the engine oil can also indicate a leaking injector, which is a serious condition that can dilute the oil and cause engine damage.
   Typical fix: Professionally clean or replace the faulty fuel injector. It's highly recommended to replace them as a matched set to ensure balanced fuel delivery.
   Est. part cost: $150-$250 per injector

Rare But Worth Checking

• Low Engine Compression: This indicates a serious internal engine issue, such as a problem with the piston rings, valves, or head gasket. A mechanical compression test is required to diagnose this and should be performed by a professional.
• Fuel Pump Failure: → Shop Fuel Pump Recall 23V-630 (Manufacturer Campaign 016G) was issued for a faulty low-pressure fuel pump in 2021-2022 GV80s, which could deform and cause a loss of motive power. While this typically causes multiple misfires (P0300) or stalling, it's a known platform issue that can affect fuel delivery.
• Carbon Buildup on Intake Valves: GDI engines can suffer from carbon accumulation on the back of intake valves since fuel is injected directly into the cylinder and doesn't wash the valves. This can disrupt airflow and cause misfires. A borescope inspection is needed to confirm.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner and confirm P0302 is active. Note if the Check Engine Light is steady or flashing. A flashing light indicates a severe misfire that could damage the catalytic converter.
2. FOR 2.5L ENGINES ONLY: Contact a Genesis dealer with your VIN to check for open campaigns. Specifically ask about Service Campaign 914G / TSB 25-01-051G for an ECM update related to misfires. If the update has not been performed, this is your primary diagnostic step.
3. If the TSB does not apply or has been completed, proceed with physical diagnosis. Locate cylinder 2. On the 2.5L I4, it is the second cylinder from the front/belt side. On the 3.5L V6, it is the front-most cylinder on the driver's side bank (Bank 2).
4. Swap the ignition coil from cylinder 2 with an adjacent, easily accessible cylinder (e.g., cylinder 1 on the 2.5T; cylinder 4 on the 3.5T). Clear the codes, start the engine, and see if the misfire code moves to the new cylinder (e.g., P0301 or P0304). If it does, the ignition coil is bad and needs replacement.
5. If the code remains on cylinder 2, inspect the spark plug. Remove it and check for excessive wear, damage, or fouling from carbon, oil, or fuel. If it looks worn or damaged, replace it. It's best to replace all plugs as a set.
6. If the coil and plug are good, the issue may be a faulty fuel injector. This is more complex and may require professional diagnosis involving fuel pressure tests or injector waveform analysis.
7. Check for any vacuum leaks around the intake manifold, as this can introduce unmetered air and cause a lean misfire.
8. If all else fails, a mechanical compression test is needed to rule out internal engine problems like worn piston rings or bad valves. This should be performed by a qualified technician.

Parts You'll Likely Need

• Engine Control Module (ECM) Reprogramming — This is the primary fix specified by Genesis for cold-start misfires on the 2.5L engine, as documented in TSB 25-01-051G.
  Trusted brands: Genesis Dealer Service
  OEM price range: $0-$200
  Aftermarket price range: N/A
• Ignition Coil (OEM #27300-2T000 (For 2.5T Engine)) — A faulty ignition coil is a very common cause for a single-cylinder misfire on any modern engine.
  Trusted brands: Genuine Genesis, Bosch, Delphi
  OEM price range: $95-$135
  Aftermarket price range: $50-$100
• Spark Plug (Iridium) (OEM #18875-09085 (Verification needed per engine)) — Spark plugs are a maintenance item that wear out over time and can cause misfires. The manufacturer recommends replacement at scheduled intervals.
  Trusted brands: Genuine Genesis, NGK, Denso
  OEM price range: $25-$40
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or begins to affect other cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may be stored alongside P0302. This can happen with fuel delivery issues or widespread carbon buildup.
• P0301, P0303, P0304 — The manufacturer TSB for the 2.5L engine specifically notes that these cylinder misfire codes can appear together due to the same ECM software sensitivity issue. They can also appear if a technician is swapping components for diagnosis.

Technical Service Bulletins (TSBs) & Recalls

• 25-01-051G / Service Campaign 914G: Addresses misfire DTCs P0300-P0304 on 2.5L T-GDI engines by providing an ECM software update to improve misfire detection logic, particularly during cold starts.

Platform-Specific Known Issues

• A known issue for models with the Theta III 2.5L T-GDI engine is the illumination of the Check Engine Light for misfire codes (P0300-P0304) during cold starts. This is addressed by manufacturer TSB 25-01-051G, which provides a corrective Engine Control Module (ECM) update.
• Multiple recalls have been issued for fuel system components on the GV80, including a failing low-pressure fuel pump (NHTSA 23V-630) and improperly sealed high-pressure fuel pipes (NHTSA 21V208000), which can lead to fuel delivery issues or leaks.

Mechanic-Grade Diagnostic Values

• OBD-II Mode $06 Misfire Counts — expected: Zero or very low counts for all cylinders during normal operation.. Failure: A significantly higher count for cylinder 2 compared to other cylinders, even if a P0302 code has not yet been set.
• Ignition Coil (Cylinder #2) Control Output — expected: A pulsing voltage signal when the engine is running. A specific ECM pinout shows an ON voltage of Max 1.1V at idle for a similar engine.. Failure: No signal or a constant voltage, indicating a problem with the ECM driver or wiring.

Scan Tool Commands That Help

• Genesis GDS (Global Diagnostic System): Power Balance Test — This function allows a technician to disable individual cylinders one by one to see the effect on engine RPM. If disabling cylinder 2 causes little or no change in RPM drop compared to other cylinders, it confirms cylinder 2 is not contributing power, pinpointing the misfire.
• Advanced OBD-II Scanner: Live Misfire Counter (per cylinder) — To observe real-time misfire events during different engine conditions (idle, acceleration, cold start). This can help determine if the misfire is constant or intermittent and under what conditions it occurs.

Wiring & Ground Locations

• ECM Pin - Injector #2 Control — On the main Engine Control Module connector. One schematic for a similar Hyundai/Genesis GDI engine identifies this as Pin 8.. This pin sends the signal to fire the fuel injector for cylinder 2. Testing for a signal here can determine if the fault is with the ECM/wiring or the injector itself.
• ECM Pin - Ignition Coil #2 Control — On the main Engine Control Module connector. One schematic for a similar Hyundai/Genesis GDI engine identifies this as Pin 49.. This pin sends the signal to fire the ignition coil for cylinder 2. Probing this pin for a correct signal helps isolate the problem between the ECM/wiring and the ignition coil.
• Main Engine Bay Ground Post — In the engine compartment, there is a designated unpainted metal bolt or post used as the negative terminal for jump-starting, as the battery is in the rear.. This is a primary chassis ground point. A loose or corroded connection here can cause various electrical issues, including weak spark that could lead to misfires.

Real Owner Repair Stories

• YouTube channel of a professional technician (Genesis GV80 3.5T (2021-2022 model year)) — Intermittent Check Engine Light with a history code for P0302. The misfire was not actively present when the vehicle was at the shop.
  ❌ Tried (didn't work) The technician initially considered an injector issue based on a prior repair on the same vehicle but decided to test the ignition system first due to the intermittent nature.
  ✅ What actually fixed it The technician swapped the ignition coil from cylinder 2 (front, driver's side) with the coil from cylinder 4 (middle, driver's side). After the customer drove the car for a week, the Check Engine Light returned with code P0304, confirming the fault had moved with the coil. Replacing the bad ignition coil resolved the issue.

OEM Part Supersession History

• 27300-2T000 → N/A — This is the current, valid OEM part number for the ignition coil on the 2.5L Turbo engine.
  Heads up: No known supersession issues or incompatibilities were found. This part is listed for 2021-2024+ GV80 2.5T models.

Model Year Variations Within This Range

• 2021-2024: Vehicles with the 2.5L T-GDI engine are subject to TSB 25-01-051G / Campaign 914G. The original ECM logic is sensitive and can falsely trigger misfire codes P0300-P0304 on cold starts. The prescribed fix is a dealer-installed software update, not a hardware change. This issue is not documented for the 3.5L Twin-Turbo V6.