P0306 on 2020-2025 Kia Telluride: Cylinder 6 Misfire Causes and Fixes (Front Bank)

What's Unique About the 2020-2025 Kia Telluride

The Kia Telluride's 3.8L Lambda II GDI V6 is a modern direct-injection engine. While generally reliable, a key detail for a P0306 code is the location of cylinder #6. Contrary to common assumptions for V6 engines, cylinder #6 is on the FRONT bank, near the radiator. This makes accessing its ignition coil and spark plug a simple task that does NOT require removing the intake manifold. The high-labor repair only applies to rear-bank codes (P0301, P0303, P0305). Some early 2020 models were also subject to TSB ENG228 for an ECM software update to correct false cold-start misfires across all cylinders.

Symptoms You May Notice

• Check Engine Light is on or flashing
• Rough or shaky idle
• Noticeable loss of power and sluggish acceleration
• Engine hesitation or stumbling
• Reduced fuel economy
• Smell of raw fuel from the exhaust

Most Likely Causes

1. Failed Ignition Coil 🔴 High Probability → Shop Ignition Coil Ignition coils are a common failure item on most modern engines due to constant heat and electrical stress.
   How to confirm: The standard diagnostic method is to swap the ignition coil from cylinder #6 with another easily accessible cylinder on the same bank (e.g., cylinder #4 or #2). Clear the codes and drive the vehicle. If the misfire code changes to P0304 or P0302, the coil is confirmed faulty. This is a very practical first step for P0306.
   Typical fix: Replace the faulty ignition coil. Since it's on the front bank, there is no need to replace other coils preventatively unless they are also failing.
   Est. part cost: $70-$110 per coil (OEM)
2. Worn or Fouled Spark Plug 🔴 High Probability → Shop Spark Plug Spark plugs are a routine maintenance item. Carbon buildup from the GDI engine can also foul plugs, leading to a weak spark.
   How to confirm: Visually inspect the spark plug after removal. Look for wear on the electrode, cracks in the porcelain, or heavy carbon/oil deposits. Given the easy access, this is a simple check.
   Typical fix: Replace the spark plug for cylinder #6. It is best practice to replace all six spark plugs if the vehicle is near its service interval, but only replacing the single plug is acceptable for a targeted fix.
   Est. part cost: $15-$25 per plug (OEM/Iridium)
3. Clogged or Faulty GDI Fuel Injector 🟡 Medium Probability → Shop Fuel Injector Gasoline Direct Injection (GDI) injectors operate under very high pressure and are susceptible to carbon buildup and failure. This is a known issue on the Lambda II engine family.
   How to confirm: This requires advanced diagnostics, such as performing a fuel injector balance test with a professional scan tool. An injector swap is not practical for DIY diagnosis as it requires removing the fuel rail.
   Typical fix: Replace the faulty fuel injector. This is an advanced job that requires special care due to the high-pressure fuel system.
   Est. part cost: $80-$120 per injector
4. Incorrect Misfire Detection (Software Issue) ⚪ Low Probability Specifically affects some 2020 Tellurides produced from Jan 9, 2019 to May 19, 2020, which could falsely detect misfires during a cold start.
   How to confirm: A Kia dealership can check the vehicle's service history and current ECU software version (ROM ID) to see if TSB ENG228 applies and has been performed.
   Typical fix: Update the Engine Control Module (ECM) with the improved logic provided in TSB ENG228. This must be done by a dealer or a qualified shop with Kia's diagnostic software.
   Est. part cost: $0 (if under warranty) or 1-hour shop labor for software update

Rare But Worth Checking

• Intake Manifold Gasket Leak: → Shop Engine Intake Manifold A vacuum leak near the intake port for cylinder #6 can lean out the air/fuel mixture and cause a misfire. This is less likely to be the cause for a single front-bank cylinder but can be checked with a smoke test.
• Low Engine Compression: A mechanical engine problem, such as a burnt valve, worn piston rings, or even a failing head gasket, can cause a persistent misfire that doesn't resolve with ignition or fuel system parts. This requires a compression test to diagnose.
• Broken Valve Spring: A specific recall (SC296 / NHTSA 24V-077) was issued for a batch of 2024 Tellurides due to defective valve springs that could break, causing loss of power and engine damage. While specific to certain 2024 models, it's a known severe mechanical failure on the platform that could present with a misfire code.

Diagnosis Steps

1. Confirm the code P0306 is present using an OBD-II scanner. Note if the check engine light is solid or flashing.
2. Check for any applicable Technical Service Bulletins (TSBs), especially TSB ENG228 for 2020 models regarding cold-start misfires.
3. Locate Cylinder #6 on the front bank of the engine (closest to the radiator, on the driver's side of the bank).
4. Swap the ignition coil from Cylinder #6 with the coil from Cylinder #4 (middle of the front bank). Clear the codes with the scanner.
5. Drive the vehicle until the check engine light returns. If the code is now P0304, the ignition coil is bad. Replace the faulty coil.
6. If the code remains P0306, the coil is likely good. Remove the coil again and inspect the spark plug for cylinder #6. Look for wear, damage, or heavy deposits. Replace the spark plug if it appears worn or fouled.
7. If the misfire persists after replacing the coil and plug, the issue may be with the fuel injector or a mechanical problem.
8. At this point, professional diagnosis is recommended. A mechanic will perform tests to check the fuel injector and measure engine compression for cylinder #6.

Parts You'll Likely Need

• Ignition Coil (OEM #27310-3L000) — This is the most common cause of a single-cylinder misfire and is easy to replace on this cylinder.
  Trusted brands: Kia (Genuine), NGK, Duralast
  OEM price range: $75-$110
  Aftermarket price range: $45-$80
• Iridium Spark Plug (OEM #18849-11070) — A worn or fouled spark plug is the second most common cause. It is a routine maintenance item.
  Trusted brands: Kia (Genuine), NGK, Denso
  OEM price range: $15-$25
  Aftermarket price range: $10-$20
• Upper Intake Manifold Gasket (OEM #29215-3L500) — NOT required for a P0306 repair. This part is only needed when accessing the rear bank for codes P0301, P0303, or P0305.
  Trusted brands: Kia (Genuine)
  OEM price range: $20-$30
  Aftermarket price range: $10-$15

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) may be stored alongside P0306.
• P0302, P0304 — Misfire codes for the other cylinders on the same bank (Bank 2, the front bank) may appear if there is a shared problem like a contaminated fuel rail affecting that side of the engine.
• P21A100 — This is a Kia-specific code for 'Cylinder #6 Air-Fuel Ratio Imbalance'. It can point directly to a failing fuel injector on that cylinder.

Technical Service Bulletins (TSBs) & Recalls

• TSB ENG228: 3.8L GDI Misfire DTC Judgment Logic Improvement: An ECU software update for 2020 Tellurides (produced from Jan 9, 2019 to May 19, 2020) to improve misfire detection logic and prevent false codes during cold starts.

Platform-Specific Known Issues

• Correct Cylinder Location is Key: The most critical piece of information for a P0306 code on this vehicle is that cylinder 6 is on the easily accessible front bank. Any diagnosis or repair quote that involves removing the intake manifold for this specific code is incorrect and should be questioned. The difficult repair is for the rear bank cylinders: 1, 3, and 5.
• Owner Experience: Cold Start Misfire: An owner of a 2020 Telluride reported a check engine light that would appear only on cold mornings, sometimes flashing, and would occasionally go away on its own. The dealer diagnosed it under TSB ENG228 and performed the software update, which resolved the problem permanently. This highlights the importance of checking for software updates before replacing parts.

Mechanic-Grade Diagnostic Values

• Long Term Fuel Trim (Bank 2) — expected: Ideally +/- 5%. Readings approaching +20% on Bank 2 (front bank) suggest a vacuum leak or underperforming injector affecting cylinders 2, 4, and 6.. Failure: A significantly high positive fuel trim on one bank indicates the ECU is adding fuel to compensate for a perceived lean condition, which can be a precursor to misfire codes.
• Valve Clearance (Intake and Exhaust) — expected: Requires adjustment every 60,000 miles (100,000 km) as a scheduled maintenance item.. Failure: Valves that are too tight will not seat properly, causing a loss of compression and a persistent misfire that will not be fixed by ignition or fuel part replacement.
• Engine Compression Ratio — expected: 13.0:1. Failure: A compression test that shows one cylinder significantly lower than others (and below the manufacturer's minimum spec) confirms a mechanical engine problem.

Hidden / Shadow Codes Worth Checking

• Mode $06 Misfire Data: Advanced scan tools can access Mode $06 data, which stores misfire counts for each cylinder from the last drive cycle, even if the count wasn't high enough to trigger a Check Engine Light. This is invaluable for confirming if a misfire is occurring on cylinder 6 after a repair attempt. (see via Professional-grade scan tool (e.g., Autel, Topdon) or some advanced consumer OBD-II apps with Mode $06 support.)

Scan Tool Commands That Help

• Kia GDS (Global Diagnostic System): ECU Upgrade — Used by dealers to apply software updates, such as the fix for TSB ENG228, which corrects false misfire detection.
• Professional Scan Tool: Power Balance Test / Misfire Counter — This live data function displays real-time misfire events for each cylinder. It's used to confirm the misfire is isolated to cylinder 6 and to verify if a repair (like a coil swap) has moved the problem to another cylinder.
• Kia GDS (Global Diagnostic System): Resetting Auto Trans Adaptive Values — While not directly for a P0306, this function is required after certain major powertrain repairs (like IVT replacement) and demonstrates the type of reset procedures that may be necessary after complex work. It's a good practice to check for any required resets after resolving a persistent misfire.

Wiring & Ground Locations

• ECM/PCM Connector — Located in the engine bay, typically a large module with multiple large wiring harness connectors.. If ignition and fuel components on cylinder 6 test good, the next step is to check for continuity and voltage at the pins on the ECM connector corresponding to the cylinder 6 ignition coil and fuel injector. A wiring diagram or pinout chart (found in resources like G6DJ Lambda II Engine Control System documents) is required to identify the correct wires to test for breaks or shorts.
• Engine Block/Cylinder Head Grounds — Multiple ground straps and wires connect the engine block and cylinder heads to the chassis/frame.. A loose or corroded engine ground can cause a weak spark across all cylinders or intermittently affect sensor readings. While it would typically cause a random misfire (P0300), a poor ground near the Bank 2 side of the engine could potentially affect cylinder 6 more than others. A visual inspection and cleaning of all major ground points is a valid diagnostic step for persistent electrical issues.

Real Owner Repair Stories

• Reddit user in r/KiaTelluride (2020 Kia Telluride, 128,000 miles) — Initial code was P0306 (Cylinder 6 Misfire).
  ❌ Tried (didn't work) Replaced the ignition coil and spark plug on cylinder 6.
  ✅ What actually fixed it The repair was ongoing, but the diagnosis changed after the initial fix. After replacing the parts, the car then threw codes for misfires on cylinders 5 AND 6, plus an O2 sensor code. Upon inspection, the owner found oil on the threads of the spark plugs for cylinders 5 and 6, indicating a likely leaking valve cover gasket was the root cause, fouling the plugs and possibly damaging the new coil.
• NHTSA ODI #11716567 — An owner reported finding internal engine failure involving a failing piston ring after experiencing codes P0300, P0302, P0304, and P0306, noting that the oil was also 1 or more quarts low.
• NHTSA ODI #11653245 — A driver reported the vehicle had very little power and difficulty maintaining speed, with a scan revealing codes P0304, P0306, P0302, P0300, and P0019, eventually rendering the vehicle undrivable.
• NHTSA ODI #11575366 — A report describes a vehicle throwing codes P0300, P0019, P0024, P0302, P0304, and P0306; upon inspection, it was discovered the engine was missing 5 quarts of oil with no warning light.

"I Checked Everything" — The Actual Cause

• In one documented case on a 2021 Telluride, a technician was chasing a misfire-like symptom and high fuel trims on Bank 2 (+12% to +20%). A smoke test for vacuum leaks came back 'perfect' with no leaks found. This ruled out a common cause for high fuel trims, forcing the diagnosis to move towards less common issues like underperforming Bank 2 fuel injectors or a faulty lambda (O2) sensor providing false readings.

When the Usual Fixes Don't Work

• While replacing the ignition coil and spark plug is the most common and effective fix, it is not a guaranteed solution. In a case with a high-mileage (128k) 2020 Telluride, a user replaced the coil and plug for P0306, only for the problem to worsen, adding a P0305 code. The underlying cause was suspected to be a leaking valve cover gasket that was fouling the spark plugs with oil. This demonstrates that if the initial fix doesn't work, the next step should be to look for secondary causes like oil leaks, fuel delivery issues, or mechanical problems, rather than assuming the new parts are faulty.

Model Year Variations Within This Range

• 2020: TSB ENG228 applies to some 2020 models produced between January 9, 2019, and May 19, 2020, for a software update to prevent false cold-start misfires.
• 2023-2025: The 2023 model year introduced a significant facelift with redesigned interior tech and exterior styling, but the 3.8L V6 powertrain and the causes/fixes for P0306 remained unchanged from 2020-2022 models.
• 2024: Recall SC296 (NHTSA 24V-077) was issued for a specific batch of 2024 Tellurides manufactured from October 1, 2023, through December 6, 2023, for defective valve springs that could break and cause engine failure, which would present as a misfire.

Documented NHTSA Reports

• NHTSA ODI #11513767: An owner reported a series of codes including P0087, P0506, P2096, P0300, P0301, P0302, P0303, P0304, P0305, and P0306 appearing intermittently.
• NHTSA ODI #11499800: A report indicates that multiple codes including P0506, P0087, P2096, P0300, P0301, P0302, P0303, P0304, P0305, and P0306 were triggered, though they occasionally cleared from the dashboard on their own.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Tow Hitch Harness Fire Risk 🔴 High — Affects 2020-2022 models equipped with the genuine Kia 4-pin tow hitch harness. (Ref: Recall SC247 / NHTSA 22V-626. Owners were advised to park outside until the repair, which involves installing a new fuse and wiring harness extension, was completed.)
• Excessive Wind Noise from A-Pillar/Windshield 🟡 Low — Common complaint from many owners of 2020+ models, often noticeable at highway speeds (55+ mph). The issue is often attributed to a less robust weatherstripping design compared to its Hyundai Palisade counterpart. (Ref: No specific recall, but some owners have had success getting weatherstripping replaced under warranty. A TSB exists for the Palisade but not explicitly for the Telluride for this issue.)
• Excessive Oil Consumption 🟠 Medium — Reported by a minority of owners, but a known issue for the 3.8L GDI engine. May not become apparent until higher mileage (50,000+ miles). Dealers may consider up to 1 quart per 1,000 miles as 'within spec'. (Ref: No specific recall, but dealers will perform oil consumption tests if the issue is reported.)
• GDI Carbon Buildup on Intake Valves 🟠 Medium — An inherent issue with all GDI engines, as fuel is injected directly into the cylinder, not over the intake valves. Typically requires cleaning (e.g., walnut blasting) every 40,000-60,000 miles to prevent misfires, rough idle, and power loss.
• Defective Valve Springs (2024 models) 🔴 High — Limited to a specific batch of 2024 Tellurides manufactured between Oct-Dec 2023. (Ref: Recall SC296 / NHTSA 24V-077. The remedy is a complete engine sub-assembly replacement.)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For a P0306 code, using used parts is generally not recommended for the most common culprits. However, if diagnosis points to a more complex failure, a used part could be considered for items like an Engine Control Module (ECM), a complete engine wiring harness, or a fuel rail assembly, provided it comes from a reputable salvage yard with a warranty and from a vehicle with verified low mileage.

Donor-vehicle mileage cap: roughly under 50000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For electronic modules (ECM), ensure no signs of water damage or corrosion on the pins.
• For wiring harnesses, inspect for any cuts, brittleness, or melted sections. Ensure all connector tabs are intact.
• Check the VIN of the donor vehicle to ensure it does not fall within any recall ranges (e.g., the 2024 valve spring recall).
• Look for a vehicle that was in a collision that did not involve the engine bay to minimize the chance of hidden damage.

OEM-only on this vehicle (don't cheap out):

• Sensors (Crankshaft, Camshaft, O2/Lambda): While aftermarket sensors exist, OEM sensors are often recommended for Kia/Hyundai vehicles to avoid compatibility and performance issues.
• Fuel Injectors: Given the precision of GDI systems, using genuine OEM injectors is the safest bet to ensure correct flow rates and spray patterns.

Aftermarket brands forum-validated for this vehicle:

• Ignition Coils: NGK, Denso
• Spark Plugs: NGK, Denso (often the OEM supplier)

Brands owners have reported issues with on this vehicle:

• Unbranded, 'white box' ignition coils and sensors from online marketplaces. These often have a high failure rate and can cause more diagnostic headaches.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0302 — A companion misfire code for Cylinder #2; often used during diagnosis when swapping ignition coils from the front bank to confirm a faulty part.
• P0304 — A companion misfire code for Cylinder #4; if a coil is swapped from Cylinder #6 to #4 and the code follows, it confirms the coil is defective.
• P0300 — A random or multiple cylinder misfire code that may accompany P0306 if issues like carbon buildup or fuel pressure affect more than one cylinder.
• P0301 — Misfire code for Cylinder #1 located on the rear bank; unlike P0306, this requires removing the intake manifold for service.
• P0303 — Misfire code for Cylinder #3 located on the rear bank; shares the same Lambda II GDi engine architecture as P0306.
• P0305 — Misfire code for Cylinder #5 located on the rear bank; shares the same Lambda II GDi engine architecture as P0306.

Frequently Asked Questions