P0304 Code: Dodge Charger (2021-2023) - Causes, Symptoms & Fixes

Diagnostic guide for OBD2 code P0304 on 2021–2023 Dodge Charger

Data note

• OWNER COMPLAINTS: No NHTSA complaints found for this make/model/year/issue combination.
• OFFICIAL RECALLS: No recalls found in NHTSA database.
• No recalls found in NHTSA database.
• Data limitations: The absence of complaints/recalls in the dataset means there is limited model-year–specific statistics for P0304. Use standard misfire diagnostics and Dodge Charger engineering knowledge to guide diagnosis.

CODE MEANING AND SEVERITY

• What P0304 means: P0304 is a misfire code indicating the engine controller detected a misfire in cylinder number 4.
• Severity and impact:
  • Immediate effects: Rough idle, reduced engine power, and potential vibration. If the misfire is severe or flashes the check engine light, driving should be limited to avoid catalytic converter damage.
  • Longer-term risks: Prolonged misfire can heat and damage a downstream catalytic converter, fouling of the spark plug, and elevated emissions. Repeated misfires can cause unburned fuel to wash the oil film and accelerate piston/cylinder wear.
• Related codes you might see alongside P0304: P0300 (random/multiple misfire), P0301, P0302, P0303, P0305, P0306 (misfires on other cylinders).

COMMON CAUSES ON DODGE CHARGER (2021–2023)

Cylinder 4 misfire can be caused by one or more of the following. The actual root cause often requires testing to confirm.

• Ignition system

  • Worn or fouled spark plug for cylinder 4.
  • Faulty ignition coil or coil-on-plug, including a bad coil boot or poor ignition coil connector.
  • Wiring harness problem or corroded/loose connector to the coil on cylinder 4.

• Fuel system

  • Faulty or dirty fuel injector for cylinder 4 (sticking open/closed or not atomizing correctly).
  • Low or unstable fuel pressure to the engine (fuel pump, fuel filter, or regulator issue).
  • Contaminated fuel or debris affecting injector operation.

• Air and vacuum

  • Vacuum leak near cylinder 4 (intake manifold gasket, hoses, or connections).
  • Intake manifold gasket issue around cylinder 4 region.
  • Carbon build-up or throttle body/vacuum issues affecting cylinder 4 intake.

• Mechanical (less common but possible)

  • Low compression in cylinder 4 due to valve seating, piston/ring wear, or a cracked/dropped valve seat.
  • Timing-related issues (rare on modern vehicles if the engine is well-maintained, but possible in severe timing component wear or failure).

• Miscellaneous

  • Dirty or faulty engine sensors affecting fuel/air trim (though P0304 is a misfire indication, sensor faults can contribute to misfire behavior).
  • PCM/ECU miscommunication or a software anomaly (less common; typically resolved with a software update if applicable).

SYMPTOMS ASSOCIATED WITH P0304

• Rough, shaking idle or engine vibrations
• Noticeable loss of power or surges during acceleration
• Decreased fuel economy
• Engine hesitation or stumble, especially at low-to-mid load
• Exhaust odors or occasional misfire watchdog activity
• MIL (Check Engine Light) on; possible misfire counter in scan tool
• In some cases, no obvious symptoms besides the MIL unless the misfire becomes severe

DIAGNOSTIC STEPS (systematic approach)

Important: Work safe, use proper PPE, and if you’re not comfortable, seek professional help. The steps below prioritize isolating cylinder 4’s misfire.

Step 0: Verify and gather data

• Use an OBD-II scanner to confirm P0304 is current. Check freeze-frame data for rpm, load, misfire counts, and sensor readings at the time of the fault.
• Check for related codes (P0300, P0301, P0302, P0303, P0305, P0306). Note any fuel trim values (short-term and long-term) that may indicate fuel delivery issues.

Step 1: Visual inspection

• Inspect spark plug for cylinder 4: fouling, oil deposits, gaps, or wear. Note if plug is wet with fuel or oil.
• Inspect ignition coil and coil boot for damage, arcing, or moisture. Check connectors for bent pins or corrosion.
• Inspect associated wiring to the coil and injector (damaged insulation, chafing, loose connectors).

Step 2: Perform a coil and plug swap test

• If the charger uses coil-on-plug ignition: swap the ignition coil from cylinder 4 to another cylinder (e.g., cylinder 2) and clear codes. Run the engine to see if the P0304 code follows the coil to the new cylinder. If the code moves with the coil, the coil is likely faulty.
• If the plug looks suspect, replace the spark plug with a new one and re-test.
• If you have multiple cylinders misfiring, address all affected cylinders.

Step 3: Inspect/test the fuel injector for cylinder 4

• Listen for a clicking injector with a mechanic’s stethoscope or long screwdriver to confirm some injector activity.
• Use a noid light to verify the injector signal from the ECU to the injector (electrical pulse).
• If accessible, swap the cylinder 4 injector with another cylinder’s injector and observe if the misfire code follows the injector.
• Consider injector cleaning if sticking or clogged; if unresolved, plan replacement.

Step 4: Check fuel system health

• Measure live fuel pressure with an appropriate gauge. Compare to the manufacturer’s spec for your engine (3.6L Pentastar and other Dodge Charger's engines have specific rail pressures; typical gasoline systems are in a certain range; consult service data for exact values).
• Inspect for signs of fuel pump or regulator issues (pulsating pressure, long crank time to start, engine surge).

Step 5: Check air and vacuum systems

• Perform a vacuum/pressure test around the intake manifold and associated vacuum hoses to look for leaks near cylinder 4’s intake path.
• Check for EGR or intake carbon buildup issues that could affect air delivery to cylinder 4.

Step 6: Check compression (mechanical health)

• With a compression tester, compare cylinder 4 compression to adjacent cylinders. Note significant deviations.
• If compression is low on cylinder 4, perform a wet compression test (add a little oil to the cylinder and re-test) to distinguish valve/seal issues from piston ring problems.
• If mechanical issues are suspected, plan further teardown or engine service.

Step 7: Revisit ignition and fuel system after initial tests

• If coil and spark plug checks pass, injector swap or fuel pressure correction may fix the issue.
• If misfire persists with all the above checks, consider more involved engine diagnostics or professional assistance.

Step 8: Confirm repair

• Clear codes and run the engine under normal driving conditions to ensure P0304 does not return.
• Monitor for new codes or retests if symptoms persist.

RELATED CODES

• P0300: Random/Multiple Cylinder Misfire Detected
• P0301: Cylinder 1 Misfire Detected
• P0302: Cylinder 2 Misfire Detected
• P0303: Cylinder 3 Misfire Detected
• P0305: Cylinder 5 Misfire Detected
• P0306: Cylinder 6 Misfire Detected
• If a misfire on a different cylinder is diagnosed, treat that cylinder’s issue similarly and consider overall engine health (e.g., fuel trim, sensor data, and drivability).

REPAIR OPTIONS AND COSTS (2025 PRICES)

Note: Prices can vary by engine variant (3.6L Pentastar V6, 5.7L Hemi V8, or 6.2L supercharged), region, and shop labor rates. The following are approximate ranges for common fixes related to a cylinder 4 misfire. All prices are ballpark estimates and assume typical shop labor rates.

• Spark plug replacement (cylinder 4)

  • Parts: $6–$25
  • Labor: 0.3–0.6 hours
  • Estimated total: $40–$140
  • Notes: If you’re addressing only cylinder 4, this is the least invasive first step if the plug looks worn or fouled.

• Ignition coil replacement (cylinder 4)

  • Parts: $40–$120
  • Labor: 0.4–0.8 hours
  • Estimated total: $120–$260
  • Notes: If the coil is suspected or confirmed bad (via swap test or visual inspection).

• Fuel injector replacement (cylinder 4)

  • Parts: $100–$250
  • Labor: 1–2 hours
  • Estimated total: $260–$650
  • Notes: Consider cleaning or replacement depending on injector condition and fuel delivery symptoms.

• Fuel system diagnostics and potential repair (pressure regulator, pump, filters)

  • Parts: $60–$600 (depending on component)
  • Labor: 1–3 hours
  • Estimated total: $200–$1200
  • Notes: If fuel pressure is abnormal or pump replacement is required, costs rise.

• Vacuum leak repair / intake gasket near cylinder 4

  • Parts: $20–$100
  • Labor: 1–3 hours
  • Estimated total: $150–$500
  • Notes: Leaks can cause persistent misfires across cylinders; fix comprehensively.

• Compression issue (valve or piston-related)

  • Parts: Varies widely; engine internal work can be expensive
  • Labor: 4–8+ hours (engine teardown)
  • Estimated total: $1000–$5000+
  • Notes: If there is a true mechanical failure in cylinder 4, repair may require significant engine work or replacement.

• ECU/PCM software update or reflash

  • Parts: $0–$200 (software/diagnostic fee)
  • Labor: 0.5–1.5 hours
  • Estimated total: $50–$300
  • Notes: Software issues are less common for misfires but can contribute in rare cases.

• General tip on pricing

  • Always request a written estimate that itemizes parts and labor.
  • If multiple components are suspect (coil + injector + plug), consider pricing options for a bundled repair to minimize downtime.

DIY VS PROFESSIONAL

• DIY-friendly steps (lower risk, lower cost)
  • Visual inspection of spark plug and ignition coil on cylinder 4.
  • Swap test: move coil to another cylinder and recheck misfire location.
  • Swap test: swap injector with another cylinder (if accessible) and monitor code changes.
  • Basic compression test with a gauge to gauge cylinder health.
  • Basic fuel pressure check with a tester (if equipped) and faucet-of-ignition checks.
• DIY limitations
  • Some 2021–2023 Charger engines use coil-on-plug arrangements with hard-to-reach spark plugs, requiring special tools.
  • Fuel pressure testing and injector testing may require precise equipment.
  • If mechanical issues or timing concerns are suspected, professional service is recommended.
• Professional route
  • A shop can perform a more thorough diagnostic: scan data analysis (fuel trim, misfire counters), cylinder balance testing, injector flow testing, ignition system diagnostics, and safe compression testing with proper tools.
  • Pros can also perform more complex repairs (valve/seat work or timing component service) with the correct procedures and torque specs.

PREVENTION

• Regular maintenance aligned with manufacturer intervals
  • Replace spark plugs at the recommended interval for your engine variant (3.6L Pentastar and other Charger engines typically have long-lived plugs, but direct-injection variants may require closer inspection; check the owner’s manual).
  • Use the correct ignition coils and spark plugs designed for your engine.
• Fuel and air quality
  • Use high-quality gasoline and keep the fuel system clean with approved fuel additives or injector cleaners as recommended.
  • Replace the air filter at recommended intervals; a clogged air filter can contribute to misfire symptoms.
• Vacuum and emissions health
  • Regularly inspect vacuum lines and hoses; fix any cracks or leaks promptly.
  • Keep the intake system clean and avoid carbon buildup that can affect cylinder performance.
• Engine care
  • Address misfires promptly to prevent catalytic converter damage; avoid prolonged driving with a known misfire.
  • Ensure regular oil changes, as low oil or degraded oil can affect engine performance and sensor readings.
• Software/updates
  • If a software update becomes available from the dealer, consider applying it after diagnosis confirms a need.

Key takeaways

• P0304 indicates a cylinder 4 misfire. The root cause could be ignition (spark plug/coil), fuel delivery (injector or pressure), air/vacuum leaks, or mechanical (compression) issues.
• A structured diagnostic approach (confirm, inspect, swap-test components, verify fuel pressure and compression) helps isolate the cause.
• Costs vary widely by cause; simple plug/coil fixes are relatively affordable, while fuel system repairs, injector work, or mechanical cylinder issues can be considerably more expensive.
• No recalls found in NHTSA database for 2021–2023 Dodge Charger related to P0304 in the provided data. No recalls found in NHTSA database.
• If you’re uncomfortable with some steps, especially pressure testing or compression testing, seek professional help to avoid unintended damage.