P0301 on 2021-2024 Genesis G80: Cylinder 1 Misfire Causes and Fixes

What's Unique About the 2021-2024 Genesis G80

For the 2021-2024 G80 equipped with the 2.5L Turbo (T-GDI) engine, this code has a very specific and well-documented cause. Genesis issued a Technical Service Bulletin (TSB 25-01-051G), as part of Service Campaign 914G, acknowledging that misfire codes (P0300-P0304) can be falsely triggered due to overly sensitive software logic, especially during cold starts. The official fix is a simple ECM software update performed by a dealer, often at no cost. This makes it a crucial first check before replacing any parts on the 2.5T model. For the 3.5L V6, while not subject to the same TSB, misfires are still common but typically point to traditional causes like ignition coils or fuel injectors.

Diagnostic Flowchart

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

Symptoms You May Notice

• Rough or vibrating idle, sometimes described as shaking.
• Hesitation or stumbling during acceleration.
• Reduced engine power and sluggish performance.
• Flashing or solid Check Engine Light.
• Decreased fuel economy.
• A smell of raw gasoline from the exhaust.

Most Likely Causes

1. Engine Control Module (ECM) Software Update Needed 🔴 High Probability Specific to the 2.5L T-GDI engine, as documented in Genesis TSB 25-01-051G. The factory software logic is too sensitive and can incorrectly flag a misfire, especially at cold start. This TSB is part of an emissions-related Service Campaign (914G).
   How to confirm: Contact a Genesis dealer and provide your vehicle's VIN. They can check if Service Campaign 914G or TSB 25-01-051G is open for your vehicle. The campaign is free of charge.
   Typical fix: Dealer performs a no-cost update of the ECM software. The service may include providing a loaner vehicle.
   Est. part cost: $0
2. Faulty Ignition Coil 🟡 Medium Probability → Shop Ignition Coil Coil-on-plug ignition coils are a common failure point on most modern engines due to constant heat and vibration. This is a frequent cause of misfires on both the 2.5T and 3.5T engines once the software update is ruled out.
   How to confirm: Swap the ignition coil from cylinder 1 with another cylinder (e.g., cylinder 2). Clear the codes and drive the car. If the code changes to P0302, the coil is bad.
   Typical fix: Replace the faulty ignition coil. This is a simple DIY job requiring basic tools.
   Est. part cost: $50-$120
3. Worn or Fouled Spark Plug 🟡 Medium Probability → Shop Spark Plug Spark plugs are a regular maintenance item. While modern iridium plugs last a long time, they can still fail, become fouled by carbon or oil, or have an incorrect gap, leading to a weak spark.
   How to confirm: After confirming the coil is good, remove the spark plug from cylinder 1. Inspect it for wear (worn electrode), damage (cracked porcelain), or heavy deposits compared to a plug from another cylinder.
   Typical fix: Replace the spark plug. It is highly recommended to replace all spark plugs as a set to maintain balanced engine performance.
   Est. part cost: $15-$40 per plug
4. Clogged or Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector Gasoline Direct Injection (GDI) systems operate under very high pressure, and injectors can become clogged or fail electronically. Some owners of platform-mates have reported injector seal failures causing misfires, leading to dealers replacing all injectors under warranty. A Genesis dealer employee noted that bad fuel injectors are a common problem on these cars.
   How to confirm: This is more difficult for a DIYer. A professional can perform a fuel injector balance test. A DIY method is to listen to the injector with a mechanic's stethoscope to ensure it's clicking. Checking the oil dipstick for a strong gasoline smell can indicate a leaking injector.
   Typical fix: Replace the faulty fuel injector. This is a more involved job than a coil or plug, especially due to the high-pressure fuel system.
   Est. part cost: $100-$250

Rare But Worth Checking

• Low Engine Compression: This indicates a serious internal engine problem, such as a worn piston ring, a bad valve, or a leaking head gasket. A compression test is needed to confirm.
• Leaking High-Pressure Fuel Pipe: A recall (Genesis 008G) was issued for some 2021 G80/GV80 models with the 2.5T engine for a fuel pipe that may not seal properly, causing a leak. While this typically causes a fuel smell, it could potentially disrupt fuel pressure and contribute to a misfire.
• Carbon Buildup on Intake Valves: This is a known long-term issue with GDI engines, including the 3.5T V6, as fuel is injected directly into the cylinder and doesn't wash over the intake valves. Over time, this can restrict airflow into the cylinder and cause misfires. This usually occurs at higher mileage and requires professional cleaning (e.g., walnut blasting).
🎬 Watch: How to clean GDI intake valves the easy way.
• Faulty Crankshaft Position Sensor: → Shop Engine Crankshaft Position Sensor A technician on a related GV70 2.5T with an intermittent P0301 misfire ultimately traced the issue to a faulty crankshaft position sensor, which was replaced to solve the problem. A failing sensor can disrupt ignition timing and cause misfires.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0301 and check for any other codes.
2. (2.5L T-GDI Engine Only) Contact a Genesis dealer with your VIN to see if TSB 25-01-051G (Service Campaign 914G) is open for your vehicle. If so, have the free ECM update performed before any other repairs.
3. If the TSB does not apply or does not fix the issue, locate cylinder 1 (front-most cylinder).
4. Swap the ignition coil from cylinder 1 with the coil from cylinder 2. Clear the codes with the scanner. Do not clear the codes if you plan to seek warranty service, as the dealer needs to see the active code.
5. Drive the vehicle until the check engine light returns. If the code is now P0302, the ignition coil is faulty and needs replacement.
6. If the code remains P0301, the coil is likely good. Swap the spark plug from cylinder 1 to cylinder 2 and repeat the process. If the code moves to P0302, the spark plug is faulty. Replace all spark plugs as a set.
7. If the code remains P0301, the issue is less likely to be a simple ignition component. Inspect the wiring and connector for the fuel injector on cylinder 1.
8. If wiring appears intact, the problem is likely a faulty fuel injector, carbon buildup, or a mechanical engine issue (low compression), which may require professional diagnosis.

Parts You'll Likely Need

• Ignition Coil (2.5L Turbo I4) (OEM #27300-2T000) — A common failure point for misfires on the 2.5T engine. This part is shared across many Hyundai, Kia, and Genesis models.
  Trusted brands: Genesis (OEM), Bosch, NGK
  OEM price range: $80-$120
  Aftermarket price range: $50-$90
• Ignition Coil (3.5L Twin-Turbo V6) (OEM #27310-3N290) — A common failure point for misfires on the 3.5T engine. Note that some sources indicate different part numbers for left and right banks.
  Trusted brands: Genesis (OEM), Delphi
  OEM price range: $90-$130
  Aftermarket price range: $60-$100
• Spark Plug (2.5L Turbo I4) (OEM #18875-09085) — A standard wear item that is a frequent cause of single-cylinder misfires.
  Trusted brands: NGK (SILZKR8J9GS), 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 affects multiple cylinders, a P0300 (Random/Multiple Cylinder Misfire) may be stored alongside P0301.
• P0302, P0303, P0304 — These codes indicate misfires in other cylinders. The TSB for the 2.5T engine specifically covers all these codes. Seeing them together could point to a systemic issue like the ECM software, low fuel pressure, or a vacuum leak.
• P0201 — This code stands for 'Injector Circuit/Open - Cylinder 1'. If you see this alongside P0301, it strongly points to a problem with the fuel injector in cylinder 1 or its wiring.

Technical Service Bulletins (TSBs) & Recalls

• 25-01-051G / Service Campaign 914G: Addresses P0300, P0301, P0302, P0303, or P0304 misfire codes on 2.5L T-GDI engines by updating the ECM software. This is noted as an emissions-related campaign.

Platform-Specific Known Issues

• A significant number of 2021-2024 G80 models with the 2.5L T-GDI engine are subject to Service Campaign 914G, which involves an ECM software update to correct false misfire detection (P0300-P0304) during cold starts.
• Owners of the platform-mate GV80 3.5T have reported frustrating dealer experiences with persistent misfires, sometimes leading to injector replacements and, in extreme cases, vehicle buybacks.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance — expected: OEM specification not found, but all injectors should measure within 0.5 Ohms of each other.. Failure: An injector that has a resistance reading more than 0.5 Ohms different from the others is likely faulty.

Hidden / Shadow Codes Worth Checking

• Misfire Counter: This is not a DTC but a live data parameter (PID) that shows a running count of misfire events per cylinder. It allows a technician to see which cylinder is misfiring and under what conditions without waiting for a DTC to set. (see via Genesis Diagnostic System (GDS) or an advanced professional scan tool with manufacturer-specific live data.)

Scan Tool Commands That Help

• GDS / Advanced Scan Tool: Cranking Cadence / Relative Compression Test — Used as a quick, non-invasive way to check for base engine mechanical problems. The tool measures variations in crankshaft speed during cranking to identify cylinders with low compression without needing a mechanical gauge.
• Advanced Scan Tool / Multimeter: Injector Activation Test — This function allows a technician to command a specific fuel injector to open and close (click). It's used to verify that the injector's solenoid is functioning electrically and is not stuck open or closed.

Real Owner Repair Stories

• Reddit user @Grouchy-Media-3831 (2023 Genesis GV70 2.5T Sport Prestige (platform-mate)) — Check Engine Light with P0303 (Cylinder 3 Misfire) at 9,000 and 12,000 miles. Vehicle had very little power, struggling to exceed 40 MPH.
  ❌ Tried (didn't work) Swapping ignition coils to different cylinders.
  ✅ What actually fixed it The Genesis dealer replaced the fuel pump, which resolved the misfire issue.
• YouTube channel '2021 Genesis GV80 how to replace igntion coil' (2021 Genesis GV80 3.5T (platform-mate)) — Intermittent misfire on cylinder 2 (P0302).
  ❌ Tried (didn't work) Initial diagnosis found an open circuit in a GDI injector which was fixed, but the misfire returned on a different cylinder weeks later.
  ✅ What actually fixed it The technician swapped the ignition coil from the misfiring cylinder 2 with the coil from cylinder 4. The misfire code then changed to P0304, confirming the ignition coil was faulty. Replacing the bad coil permanently fixed the problem.
• Reddit user 'deleted' (Genesis GV70 (year/engine not specified, but context implies 2.5T)) — Check Engine Light with code P030100. Vehicle was reportedly running fine otherwise.
  ❌ Tried (didn't work) Owner was struggling to get service from the dealership.
  ✅ What actually fixed it Another user commented with authority, 'It needs injectors.' This aligns with other reports that fuel injectors are a known failure point for this code after the TSB and ignition components are ruled out.

When the Usual Fixes Don't Work

• While the TSB for an ECM update is the most common fix for a P0301 on the 2.5T engine, it is not a guaranteed solution. A real-world repair story on a 2023 GV70 2.5T showed that even after trying common diagnostic steps like swapping coils, the ultimate culprit was a faulty fuel pump, which was replaced by the dealer to solve the misfire. This indicates that for the 2.5T, if the software update does not resolve the issue, a hardware problem with the fuel delivery system should be considered a primary suspect before assuming more complex engine mechanical issues.