P0306 on 2024 Ford F-250: Cylinder 6 Misfire Causes and Fixes

What's Unique About the 2024-2024 Ford F-250

While a misfire can be simple, on the F-250 platform it requires careful diagnosis due to engine-specific issues. The 7.3L 'Godzilla' V8 is known for spark plug wires that fail prematurely from exhaust manifold heat, a problem Ford has acknowledged with service bulletins on related platforms like the F-53 Motorhome chassis. More critically, for both the 6.8L and 7.3L gas engines, a misfire code can sometimes be the first symptom of a significant internal engine problem related to camshaft and lifter wear. This wear is linked to the variable displacement oil pump's low-pressure strategy at idle. Ford has issued Customer Satisfaction Program 24B27 to reprogram the PCM for increased idle oil pressure to mitigate this. Therefore, a P0306 code should be investigated thoroughly, starting with simple ignition components but keeping the potential for more serious issues in mind.

Symptoms You May Notice

• Rough or shaking idle
• Engine hesitation or stumbling during acceleration
• Noticeable loss of power
• Flashing Check Engine Light
• Possible engine tapping or ticking noise (indicative of potential valvetrain issues)
• Engine running rougher when towing or under heavy load

Most Likely Causes

1. Faulty Spark Plug Wire (7.3L Gas Engine) 🔴 High Probability → Shop Spark Plug The spark plug wires on the 7.3L 'Godzilla' V8 are routed near the hot exhaust manifolds, causing the boots to degrade, crack, and arc. This is a widely documented issue and the subject of Ford TSB 20-2370 on related platforms, which notes failures on vehicles with very low mileage. Aftermarket companies offer high-temperature ceramic boot wires specifically to solve this problem.
   How to confirm: Visually inspect the spark plug wire and boot for cylinder 6 for any signs of melting, cracking, or white ash 🎬 Watch: How to diagnose and solve a common Godzilla misfire. (arcing). A common test is to swap the cylinder 6 wire with another cylinder (e.g., cylinder 8) and see if the misfire code changes to P0308.
   Typical fix: Replace the faulty spark plug wire. It is often recommended to replace all 8 wires with an updated OEM set or a higher-quality 🎬 Watch: Step-by-step guide to replacing Godzilla spark plugs and wires. aftermarket set designed for better heat resistance, often featuring ceramic boots.
   Est. part cost: $25-$200 for a full set
2. Faulty Ignition Coil (All Gas Engines) 🔴 High Probability → Shop Ignition Coil Coil-on-plug (or coil-near-plug) systems are common failure points on most modern vehicles due to constant exposure to engine heat and vibration.
   How to confirm: Swap the ignition coil from cylinder 6 with another cylinder (e.g., cylinder 5 on the driver's side). Clear the codes and drive the vehicle. If the code changes to P0305, the ignition coil is faulty. This is the most common DIY diagnostic step.
   Typical fix: Replace the ignition coil for cylinder 6.
   Est. part cost: $40-$90
3. Worn or Fouled Spark Plug (All Gas Engines) 🟡 Medium Probability → Shop Spark Plug
   How to confirm: After ruling out the coil and wire, remove the spark plug from cylinder 6. Inspect it for wear on the electrode, excessive carbon buildup, oil fouling, or damage to the ceramic insulator.
   Typical fix: Replace the spark plug. If the vehicle has high mileage, it is best practice to replace all spark plugs at the same time.
   Est. part cost: $8-$15 per plug
4. Faulty Fuel Injector ⚪ Low Probability → Shop Fuel Injector While less common on gas engines, a clogged or failed fuel injector can cause a lean misfire. This is a much higher probability cause on the 6.7L Power Stroke diesel engine.
   How to confirm: This is more difficult to diagnose. A professional can perform a fuel injector balance test. A DIY method involves listening to the injector with a mechanic's stethoscope to ensure it's clicking consistently.
   Typical fix: Replace the fuel injector for cylinder 6.
   Est. part cost: $50-$150 (gas), $200-$400+ (diesel)

Rare But Worth Checking

• Worn Camshaft and/or Valve Lifters (6.8L & 7.3L Gas): → Shop Engine Camshaft This is a serious mechanical issue. If you hear a persistent ticking or tapping noise 🎬 See what a 7.3L lifter failure sounds like in person. from the engine along with the misfire, this is a strong possibility. The root cause is often attributed to the Variable Displacement Oil Pump (VDOP) operating at very low pressure during idle, leading to insufficient lubrication and wear (spalling) of lifters and cam lobes. Ford has issued Customer Satisfaction Program 24B27 to update the PCM software, which increases idle oil pressure to prevent this wear. TSB 23-2334 also addresses misfire codes caused by this valvetrain wear. Diagnosis requires a compression test and may require professional inspection of the valvetrain, which can be a significant repair if the engine has already sustained damage.
• Engine Harness Interference: A manufacturer service bulletin notes that some vehicles may exhibit an illuminated MIL with DTCs P0301-P0306 due to the engine harness contacting a hose crimp end or spring clip (TSB 25-2569).
• Exhaust System Restrictions: A manufacturer bulletin for related Ford platforms suggests that a misfire condition with P0300 through P0306 can be caused by internal components of the muffler being assembled improperly (TSB 19-2286).

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0306 is the primary code. Note any other codes like P0300 or P0316.
2. Check for any applicable Technical Service Bulletins (TSBs) or Customer Satisfaction Programs for your vehicle's VIN. Specifically inquire about CSP 24B27 and TSB 25-2569 regarding engine harness contact.
3. (7.3L Engine) Carefully inspect the spark plug wire for cylinder 6 (second from front, driver's side) for signs of heat damage, melting, cracking, or arcing near the boot.
4. Swap the ignition coil from cylinder 6 with cylinder 5 (front-most on the driver's side). Clear the codes, drive the truck, and see if the code returns as P0305. If it does, the coil is bad.
5. (7.3L Engine) If the coil swap has no effect, swap the spark plug wire from cylinder 6 with cylinder 8 (rear-most on the driver's side). If the code changes to P0308, the wire is bad.
6. If the misfire remains on cylinder 6, remove and inspect the spark plug for wear, fouling, or damage. Replace it if necessary.
7. If ignition components are good, listen for a consistent ticking or tapping noise from the engine, especially at idle. If present, this strongly suggests a valvetrain issue.
8. A compression test is the next step to check for internal mechanical issues. A low reading on cylinder 6 points towards a problem like a worn cam/lifter or a valve sealing issue.
9. If compression is good, the issue may be a clogged fuel injector, which may require professional diagnosis.

Parts You'll Likely Need

• Ignition Coil (OEM #PC3Z-12029-AA (supersedes DG-589, PC3Z-12029-A)) — A primary cause of misfires on all gas engines due to heat and vibration. This part fits both 6.8L and 7.3L engines.
  Trusted brands: Motorcraft, NGK, MSD
  OEM price range: $60-$90
  Aftermarket price range: $40-$70
• Spark Plug Wire Set (7.3L Engine) (OEM #LC3Z-12286-C (updated part)) — A known weak point on the 7.3L 'Godzilla' engine due to heat degradation from the exhaust manifold. TSB 20-2370 specifies replacing all 8 wires.
  Trusted brands: Motorcraft, MSD, Taylor, OBR Control Systems, Granatelli
  OEM price range: $100-$150
  Aftermarket price range: $80-$250 (High-temp ceramic boot versions are more expensive)
• Spark Plug (OEM #CYFS-12Y-T6 (Motorcraft SP-589)) — A standard maintenance item that can wear out and cause misfires.
  Trusted brands: Motorcraft, NGK, Autolite
  OEM price range: $10-$15
  Aftermarket price range: $7-$12

Related Codes That Often Appear With This One

• P0300 — If the misfire becomes more widespread or is intermittent across multiple cylinders, a P0300 (Random Misfire) code may appear alongside the P0306.
• P0316 — Misfire Detected on Startup (First 1000 Revolutions). This code often appears with a specific cylinder misfire code and is mentioned in TSB 20-2370 related to the 7.3L engine.

Technical Service Bulletins (TSBs) & Recalls

• TSB 23-2334: Notes that P030x misfire codes on 7.3L engines can be caused by excessive wear on the camshaft and/or valve tappets (lifters). This TSB supersedes a previous version.
• TSB 20-2370: Addresses misfires (P0300, P0301-P0304) on 7.3L engines in F-53 Motorhome chassis caused by heat-damaged spark plug wires, confirming it's a known issue with the part design and routing. The fix involves replacing all 8 wires.
• TSB 25-2569: States that some vehicles may exhibit an illuminated MIL with DTCs P0301-P0306 due to the engine harness contacting a hose crimp end or spring clip.
• TSB 19-2286: Notes that a misfire condition with DTC P0300 through P0306 may be due to internal components of the muffler being assembled improperly on certain high-output engines.
• Customer Satisfaction Program 24B27: PCM software update for 2020-2024 Super Duty and E-Series with 6.8L/7

Platform-Specific Known Issues

• Gas Engines (6.8L/7.3L): A customer satisfaction program (24B27) was issued to update the PCM software. The original calibration of the variable displacement oil pump could lead to excess wear on camshafts and valve tappets during prolonged idle, potentially causing misfires and engine noise.
• 7.3L Gas Engine: Prone to spark plug wire failure due to high heat from the exhaust manifold, as documented in TSB 20-2370 for similar applications. Aftermarket solutions with ceramic boots are a popular upgrade.
• 6.7L Diesel Engine: Misfires are most commonly linked to piezoelectric fuel injector failures or, less commonly, valvetrain issues like collapsed lifters.

Mechanic-Grade Diagnostic Values

• Ignition Coil Primary Resistance (7.3L 'Godzilla') — expected: 0.53 Ohms (MSD aftermarket example). Failure: Significant deviation from the spec of a known-good coil, or an open/short circuit reading.
• Ignition Coil Secondary Resistance (7.3L 'Godzilla') — expected: 13.7K Ohms (MSD aftermarket example). Failure: Significant deviation from the spec of a known-good coil.
• Ignition Coil Primary Resistance (6.8L V8) — expected: ~0.510 - 0.73 Ohms (aftermarket examples). Failure: A reading of infinity (open circuit) or zero (short circuit) indicates a failed coil.
• Fuel Injector Resistance (7.3L 'Godzilla') — expected: 12.5 Ohms (Bosch EV14 OEM example). Failure: Significant deviation from specification.
• Fuel Injector Minimum Pulse Width (7.3L 'Godzilla') — expected: Will maintain consistency down to 1.4 ms. Failure: Inconsistent operation below this threshold could indicate a failing injector.
• Spark Plug Wire Resistance (7.3L 'Godzilla') — expected: ~30-500 Ohms per foot, depending on brand (e.g., Scott Performance 30 Ohm, TSP 500 Ohm).. Failure: Extremely high resistance or an open circuit (infinite resistance) indicates a broken wire.

Hidden / Shadow Codes Worth Checking

• Mode $06, Test ID $A2-$A7: Mode $06 data allows viewing of misfire counts per cylinder before they reach the threshold to trigger a Check Engine Light. For a V8, Test IDs $A2 through $A9 typically correspond to cylinders 1 through 8. Monitoring the count for Test ID $A7 (Cylinder 6) can confirm an intermittent misfire that hasn't yet set code P0306. (see via A professional scan tool or a quality consumer OBD-II scanner with Mode $06 capability.)

Scan Tool Commands That Help

• Ford IDS (Integrated Diagnostic System): Power Balance Test — This bidirectional test allows a technician to disable one cylinder at a time and observe the corresponding drop in RPM. If disabling cylinder 6 results in little or no change in engine speed, it confirms that cylinder is not contributing power, validating the P0306 code and helping to isolate the issue in real-time.

Wiring & Ground Locations

• G104 (Left Rear of Engine Compartment) — Located on the driver's side, at the rear of the engine compartment, often on the firewall or inner fender area.. This is a primary engine compartment ground. A loose or corroded G104 can cause a host of issues, including weak spark or erratic sensor readings that could lead to misfire codes. It serves as a ground point for various engine components, potentially including the PCM or ignition system components.
• PCM Ground — The Powertrain Control Module (PCM) has multiple ground pins in its main connector. The specific pin for the cylinder 6 coil driver ground would be found in a factory wiring diagram.. The PCM provides the ground path to fire the ignition coil. An internal PCM fault or a problem with the ground pin for the cylinder 6 coil driver circuit would prevent the coil from firing, causing a P0306. This is a rare failure but should be considered after all external wiring and components have been verified.
• Engine Block to Chassis/Body Ground Straps — Multiple straps connect the engine block to the vehicle's frame and body. One key location is from the back of the cylinder head to the firewall; another runs from the engine block near the starter to the frame.. A poor engine ground forces the ignition system's return path to find other, less efficient routes, which can result in a weak spark and misfires, especially under load. Ensuring these main grounds are clean and tight is a crucial step in diagnosing any electrical issue, including misfires.

Real Owner Repair Stories

• Reddit user @Radiant-Position-463 (2024 Ford F-250 w/ 7.3L Gas Engine) — After being parked for two weeks in -14°F weather, the truck had a rough cold start and later threw a check engine light. Codes P0300, P0313, and P0316 were present. The engine seemed to run fine once warmed up at normal idle RPM.
  ❌ Tried (didn't work) Filling the fuel tank, suspecting water/condensation, did not resolve the issue.
  ✅ What actually fixed it The user did not post the final resolution, but the symptoms point towards a common scenario where extreme cold can cause temporary issues with ignition components or fuel. The primary advice given was to take it to the dealer under warranty, as an engine misfire is typically a spark plug or coil pack failure.
• Ford Truck Enthusiasts Forum user 'Sidedge' (2022 F-250 w/ 7.3L Gas Engine, 98k miles) — Rough idle with no trouble codes, but misfires were visible on multiple cylinders using Mode 6 data. Hesitation/stumble during acceleration when cold.
  ❌ Tried (didn't work) Replaced spark plugs with Motorcraft parts., Replaced spark plug wires and coils with the newest OEM versions., Cleaned the MAF sensor., Cleaned the throttle body (which seemed to increase misfires).
  ✅ What actually fixed it The thread did not have a final confirmed fix, but the user was advised to check eligibility for the low oil pressure reflash (CSP 24B27) and another user noted that these engines often show high misfire counts in Mode 6 data without apparent running issues. The unresolved nature points to the complexity of diagnosing issues that don't set a hard code, potentially leaning towards the known valvetrain concerns.

Documented NHTSA Reports

• An owner reported a flashing check engine light and deceleration where the dealership authorized a long block engine change for a P0306 code (NHTSA ODI #11042915).
• A report describes a P0306 misfire occurring after driving in heavy rain for several hours (NHTSA ODI #10658587).
• One owner reported that a mechanic diagnosed P0302 and P0306 codes and determined that coolant was leaking into the engine block (NHTSA ODI #11621299).

Diagnostic Flowchart

Other Known Issues on This Vehicle

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

• 10R140 Transmission Faults 🔴 High — Commonly reported. Issues include harsh/erratic shifting, sudden downshifts, delayed engagement, and internal failure of the C-D-F drum assembly, sometimes requiring full replacement shortly after warranty expiration. (Ref: SSM 51420 notes delayed engagement is a 'normal characteristic'. CSP 24B05 was issued for a small number of 2023 trucks for missing main control assembly bolts.)
• Water Intrusion in Tailgate Camera/Module 🟠 Medium — Widespread enough to trigger a recall. (Ref: Recall 24S66: Water can enter the Tailgate Park Assist Sensor Interface Module (TPASIM), causing the rearview camera image to fail. The fix involves replacing the camera, harness, and module.)
• Loss of Trailer Lights/Brakes 🔴 High — Affects a wide range of Ford trucks and SUVs. (Ref: Recall 26C10: The integrated trailer module (ITRM) may lose communication, causing a loss of trailer brake and turn signal lights. A software update is required.)
• Body Panel Misalignment and Poor Fit/Finish 🟡 Low — Frequently mentioned by owners of 2023+ models, particularly regarding hood, door, and bed alignment from the factory.
• SYNC 4 Infotainment Glitches 🟡 Low — Various issues reported, including screen freezing, USB errors during updates, and connectivity problems with Apple CarPlay. (Ref: Multiple TSBs exist, such as SSM 52328 (USB Error during programming) and SSM 52370 (CarPlay connectivity).)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this very new vehicle (2024), using used parts is generally not recommended unless for a major component like a complete engine assembly where a low-mileage donor is available from a wreck. For a P0306, the common failure items (coils, wires, plugs) are relatively inexpensive new, and their wear-and-tear nature makes used parts a poor value proposition.

Donor-vehicle mileage cap: roughly under 30000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For an ignition coil, check for cracks in the housing or epoxy.
• For spark plug wires, ensure boots are pliable with no cracks, and check for white 'ash' marks indicating arcing.
• Verify the donor vehicle's VIN to ensure it wasn't subject to unresolved recalls or the lifter issue.

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

• Powertrain Control Module (PCM) - Requires VIN-specific programming that makes used modules difficult to implement.
• Fuel Injectors - While aftermarket exists, OEM Bosch injectors are recommended for consistent performance and compatibility with factory tuning.

Aftermarket brands forum-validated for this vehicle:

• Spark Plug Wires (7.3L): OBR Control Systems, MSD, Granatelli, Scott Performance Wire, and other brands offering high-temperature ceramic or silicone boots are considered significant upgrades over the stock wires.
• Ignition Coils: MSD is a well-regarded performance aftermarket brand for this application.

Brands owners have reported issues with on this vehicle:

• Generic, unbranded ignition coils and spark plug wires from online marketplaces often have poor quality control and may fail prematurely or offer inconsistent performance.

Real Owner Stories

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

Related OBD-II Codes

• P0300 — Random or multiple cylinder misfire code that often accompanies a specific cylinder code like P0306 when multiple spark plug wires are degraded by heat.
• P0305 — Misfire on cylinder 5; often appears during diagnostics if the ignition coil is swapped from cylinder 6 to cylinder 5 to test for a component failure.
• P0308 — Misfire on cylinder 8; typically appears during diagnostics if the spark plug wire is swapped from cylinder 6 to cylinder 8 to confirm a faulty wire.
• P0316 — Misfire detected on startup (first 1000 revolutions), which may be noted alongside P0306 during initial OBD-II scanning.

Frequently Asked Questions