P0300 on 2022-2025 Genesis GV70: Random Misfire Causes and Fixes

What's Unique About the 2022-2025 Genesis GV70

The most significant issue for the Genesis GV70 with the 2.5L Turbo engine is a known software problem. Genesis issued a Technical Service Bulletin (TSB 25-01-051G) because the original ECM software is overly sensitive and can incorrectly report misfires (P0300 and others like P0301-P0304), particularly during a cold start. Many owners who might otherwise suspect bad spark plugs or coils can resolve the issue with a simple, free software update at a dealership. This makes checking for the TSB the absolute first step in diagnosis. This engine also features a dual injection system (GDI and MPI), which can sometimes complicate diagnosing fuel-related misfires.

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 shaky engine idle, especially on cold start
• Engine hesitation or stumbling during acceleration
• Reduced engine power and poor acceleration
• Poor fuel economy
• A noticeable smell of gasoline from the exhaust
• Fuel smell in engine oil (a critical symptom of a leaking GDI injector)

Most Likely Causes

1. Engine Control Module (ECM) Software Update Needed 🔴 High Probability → Shop Engine Control Module (ECM) As documented in TSB 25-01-051G, the factory ECM software has overly sensitive misfire detection logic, especially on cold starts. This is a widely reported issue for the 2.5L T-GDI engine across multiple Genesis models. The California Air Resources Board determined these vehicles could release excess pollutants due to this issue.
   How to confirm: Contact a Genesis dealership and provide your vehicle's VIN. They can confirm if Service Campaign 914G (related to TSB 25-01-051G) is open for your vehicle. The campaign applies to specific production dates, for example, 2022-2025 GV70 (JK1) models produced from 03/29/2021 – 03/04/2025.
   Typical fix: A Genesis dealer performs a software update on the ECM and applies an emission sticker. This service is performed for free under the service campaign.
   Est. part cost: $0
2. Worn or Defective Spark Plugs 🟡 Medium Probability → Shop Spark Plug Spark plugs are a standard maintenance item. While not a specific defect, they are a common cause of misfires on any gasoline engine as they wear out, leading to a weak or inconsistent spark.
   How to confirm: Remove and inspect the spark plugs. Look for worn or melted electrodes, cracks in the porcelain, or heavy carbon/oil fouling. Replace them if they are near their recommended service interval.
   Typical fix: Replace all four spark plugs as a set. It is recommended to use OEM plugs (Part No. 18875-09085) or equivalent quality NGK plugs.
   Est. part cost: $80-$120
3. Faulty Ignition Coils 🟡 Medium Probability → Shop Ignition Coil Ignition coils can fail over time due to heat and vibration, leading to a weak or non-existent spark. This is a common failure point for misfires across many modern vehicles. Some owners report intermittent rough idles on cold starts as an early symptom.
   How to confirm: If you have a specific cylinder misfire code (e.g., P0301) along with P0300, swap the ignition coil from the misfiring cylinder with one from a known good cylinder. Clear the codes and run the engine. If the code follows the coil (e.g., changes to P0302) 🎬 See a real-world diagnosis of a P0304 misfire code., the coil is bad.
   Typical fix: Replace the faulty ignition coil. The OEM part number is 27300-2T000. Many technicians recommend replacing all coils if they are original and the vehicle has higher mileage.
   Est. part cost: $50-$90 per coil
4. Clogged or Faulty Fuel Injectors ⚪ Low Probability → Shop Fuel Injector Direct injection (GDI) engines can be susceptible to carbon buildup, and there are numerous owner reports of premature fuel injector failure on the 2.5T engine. Some owners have experienced long backorder waits for replacement parts, suggesting a common issue.
   How to confirm: This is difficult for a DIYer. A critical sign is an engine oil level that is rising and smells strongly of gasoline, which indicates a leaking injector is diluting the oil. A professional can perform an injector balance test or use a scan tool to monitor fuel trim data for abnormalities.
   Typical fix: The faulty injector(s) must be replaced. In many documented cases, dealers have replaced all four injectors under warranty to resolve the issue. This is a critical repair, as a leaking GDI injector can lead to catastrophic engine failure. The OEM part number for the fuel injector is 35310-2T000.
   Est. part cost: $100-$200 per injector

Rare But Worth Checking

• Failing Low-Pressure Fuel Pump: → Shop Fuel Pump A recall (NHTSA Campaign 23V630000, also known as Genesis recall 022G) was issued for a failing low-pressure fuel pump that can cause a loss of power. While this may not always set a P0300 code, the symptoms of engine hesitation and power loss can be similar to a misfire.
• Vacuum Leak: A leak in a vacuum hose or intake manifold gasket can introduce unmetered air into the engine, throwing off the air-fuel ratio and causing random misfires. A smoke test is the most effective way to find a leak.
• Faulty Crankshaft Position Sensor: → Shop Engine Crankshaft Position Sensor An intermittent failure of the crankshaft position sensor can cause false misfire codes. In one documented case on a 2.5T GV70, a technician found that a glitchy sensor signal, particularly on a cold start, was the true cause 🎬 Watch: A technician diagnoses a persistent cylinder 1 misfire. of a persistent P0301 after plugs and coils were ruled out.
• Intake Valve Carbon Buildup: Gasoline Direct Injection (GDI) engines do not spray fuel over the intake valves, which allows oil vapor and combustion byproducts to bake onto the valves over time. This buildup can disrupt airflow at idle, causing random, lean misfires that trigger a P0300 code. This is more common on vehicles that are frequently driven for short trips. The fix is a mechanical cleaning, often called walnut blasting.

Diagnosis Steps

1. Check for Service Campaigns: First, call a Genesis dealership with your VIN to see if Service Campaign 914G for the ECM misfire logic is open for your vehicle. This is the most likely and cheapest fix.
2. Scan for All Codes: Use an OBD-II scanner to read all stored codes. Note any specific cylinder misfire codes (P0301-P0304) as they will guide your diagnosis. Using a dealer-level tool like GDS Mobile can provide more detailed misfire data and history.
3. Assess the Check Engine Light: If the light is flashing, do not drive the vehicle. A flashing MIL (Malfunction Indicator Lamp) signals a severe misfire that can damage the catalytic converter.
🎬 Watch: A helpful guide on fixing random P0300 codes.
4. Check Engine Oil: Carefully pull the dipstick and check for a rising oil level or a strong smell of raw gasoline. If detected, do not run the engine. This points to a serious fuel injector leak.
5. Inspect Spark Plugs: If the ECM update is not needed or has been done, inspect the spark plugs. Look for wear, damage, or fouling. Replace if they are worn or if their service interval has been reached.
6. Test Ignition Coils: If a specific cylinder is misfiring, swap its ignition coil with another cylinder's coil. Clear the codes and run the engine. If the misfire code moves to the new cylinder, the coil is faulty and needs replacement.
7. Check for Vacuum Leaks: Visually inspect all vacuum hoses for cracks or disconnection. For hard-to-find leaks, a smoke test is the most effective method.
8. Advanced Fuel System/Sensor Diagnosis: If the above steps do not resolve the issue, the problem may be in the fuel system (injectors, pump) or a faulty sensor like the crankshaft position sensor. This level of diagnosis requires professional tools and is best left to a qualified technician.

Parts You'll Likely Need

• ECM Software Update — This is the most common fix for P0300 on the 2.5T GV70, addressing a known issue with misfire detection logic per TSB 25-01-051G.
  OEM price range: $0 (under campaign)
  Aftermarket price range: N/A
• Spark Plugs (OEM #18875-09085) — Spark plugs are a routine maintenance item and a primary cause of misfires when worn.
  Trusted brands: Hyundai/Genesis OE, NGK
  OEM price range: $20-$30 per plug
  Aftermarket price range: $15-$25 per plug
• Ignition Coil (OEM #27300-2T000) — An ignition coil failure results in a lack of spark to the cylinder, directly causing a misfire.
  Trusted brands: Hyundai/Genesis OE, Delphi, Denso
  OEM price range: $70-$100
  Aftermarket price range: $40-$70

Related Codes That Often Appear With This One

• P0301, P0302, P0303, P0304 — These codes indicate a misfire on a specific cylinder (1, 2, 3, or 4). P0300 often appears with one or more of these codes, which helps narrow down the location of the problem.
• P0171, P0172 — These codes for 'System Too Lean' or 'System Too Rich' can appear alongside P0300 if the misfire is caused by a fuel delivery issue or a major vacuum leak.

Technical Service Bulletins (TSBs) & Recalls

• 25-01-051G: Describes the procedure for updating the ECM software to correct false misfire detection (P0300, P0301-P0304) on 2.5L T-GDI engines as part of Service Campaign 914G.

Platform-Specific Known Issues

• Service Campaign 914G / TSB 25-01-051G: Genesis identified that the ECM on 2.5L T-GDI engines may incorrectly detect misfires and set codes P0300-P0304, especially during cold starts. The fix is a no-cost software update at a dealership. This campaign covers vehicles within specific production date ranges.

Hidden / Shadow Codes Worth Checking

• Mode $06 Misfire Data: This is not a typical DTC but a function within an advanced scan tool that shows raw misfire counts per cylinder for the current and previous driving cycles. It can reveal which cylinder is misfiring even if a specific P030x code has not yet been set. For example, seeing 100 misfire counts on cylinder 4 while others have zero confirms the problem location before a P0304 is stored. (see via An advanced OBD-II scanner with Mode $06 capability, such as a BlueDriver or a professional-grade tool like Autel or the dealer GDS Mobile.)

Scan Tool Commands That Help

• Genesis GDS: Event #1260: JK1(A) THETA3 2.5T-GDI FR MISFIRE DTC (P030X) IMPROVEMENT — This is the specific software update event a Genesis dealer technician selects to re-flash the Engine Control Module (ECM) with the improved misfire detection logic as prescribed by TSB 25-01-051G to fix false P0300 codes.

Wiring & Ground Locations

• Engine Block to Body Ground Strap — Typically a braided metal strap connecting the engine block or cylinder head to the vehicle's chassis/firewall. While exact GV70 locations require a service manual, common points are from the back of the engine block to the body.. A poor engine ground can cause a host of phantom electrical issues, including weak spark or erratic sensor readings, which can lead to misfires. The ignition coils rely on a solid ground to function correctly. Verifying this connection is clean and tight is a fundamental step in diagnosing electrical-related misfires.
• Jump Starting Negative (-) Ground Point — The GV70 owner's manual specifies a dedicated chassis ground point in the engine compartment for jump-starting, separate from the battery which is in the cargo area.. While not directly for diagnostics, knowing the official, safe ground point is critical for any electrical testing that requires a chassis ground reference, preventing damage to sensitive electronics.

Real Owner Repair Stories

• Reddit user in /r/GenesisGV70 (2023 Genesis GV70 with 13,000 miles) — Check Engine Light came on and the engine went into a safety/limp mode. The code was P030100 (Cylinder 1 misfire).
  ❌ Tried (didn't work) The user took the vehicle directly to the dealer.
  ✅ What actually fixed it The dealer replaced all four fuel injectors under warranty. The service department noted they had seen cases where the injector seal expands due to temperature changes, causing irregular fuel flow and misfires.

Model Year Variations Within This Range

• 2024-2025: The GV70 is built in two locations. Korean-built models have a VIN starting with 'KMU', while USA-built (Montgomery, Alabama) models have a VIN starting with '5NM'. The ECM update campaign (914G) has different production date ranges for each plant, so providing the VIN to the dealer is essential to confirm eligibility. For example, the campaign covers 2024-2025 '5NM' GV70s produced from 05/10/2023 – 02/13/2025.