P0304 Code: Dodge Ram 1500 (2019-2024) - Causes, Symptoms & Fixes

Below is a comprehensive diagnostic guide for OBD2 code P0304 (Cylinder 4 misfire detected) focused on the 2019–2024 Dodge Ram 1500. Data provided: NHTSA owner complaints and recalls lists for this model/years show no complaints and no recalls in the database. No recalls found in NHTSA database.

1. CODE MEANING AND SEVERITY

• What P0304 means: P0304 is a cylinder-specific misfire code. It indicates that the Powertrain Control Module (PCM) detected that cylinder 4 did not complete its combustion as expected. In other words, the cylinder is misfiring.
• Severity and consequences:
  • Mild/momentary misfires may cause rough idle or stumble but can be tolerated briefly.
  • Persistent misfires can cause rough running, loss of power, increased fuel consumption, elevated emissions, and potential damage to the catalytic converter if not corrected.
  • Some Ram 1500s will default to a limp/limited power mode if misfire is persistent to protect the catalytic converter; this can reduce performance.
• Related behavior to watch for:
  • Check Engine Light (CEL) on, possibly with a P0304 code stored and possibly P0300 (random misfire) in memory if the PCM has trouble isolating the fault.
  • Misfire might be more noticeable at idle, during acceleration, or at certain engine loads/RPMs.

2. COMMON CAUSES ON DODGE RAM 1500 (2019–2024)

• Faulty ignition components on cylinder 4:
  • Worn or fouled spark plug in cylinder 4.
  • Faulty ignition coil on cylinder 4 or a bad coil boot/connector.
• Fuel delivery issues for cylinder 4:
  • Clogged or leaking fuel injector for cylinder 4.
  • Low or unstable fuel pressure affecting cylinder 4.
• Air and vacuum-related issues:
  • Vacuum leak or cracked/brittle intake hoses around the intake manifold or the cylinder 4 runner.
  • PCV valve or PCV hose issues.
• Compression and mechanical problems:
  • Low compression in cylinder 4 due to worn piston rings, burnt valve, bad valve seat, head gasket issue, or timing-related problems.
  • Timing chain/belt wear or camshaft/phaser issues (rarely isolated to cylinder 4, more often across multiple cylinders).
• Miscellaneous:
  • Dirty or contaminated fuel causing ignition or lean misfire symptoms.
  • Dirty MAF/MAF sensor or degraded MAP sensor causing improper air-fuel mixture (usually shows other codes too).
  • Exhaust or misrouting issues that affect exhaust backpressure (less common for a single-cylinder misfire).

3. SYMPTOMS ASSOCIATED WITH P0304

• Engine runs rough or shakes at idle; noticeable misfire.
• Power loss or hesitation during acceleration; reduced towing capability.
• Increased fuel consumption and possibly strong fuel odor (unburned fuel entering the exhaust).
• Check Engine Light with P0304 (and possibly P0300 if multiple misfires are detected).
• Infrequent cold-start roughness or spark misfire after engine heat soak.
• No overheating; typical engine temperatures unless the misfire triggers other engine problems.

4. DIAGNOSTIC STEPS (step-by-step approach)
   Note: This is a practical, field-oriented workflow. Work safely, with the engine off when removing ignition components, and only operate components you are comfortable handling. Use a quality scan tool capable of live data, misfire counters, and injector/ignition diagnostics.

Step 1 — Verify the code and data

• Read PCM codes with a capable OBD-II scanner. Confirm P0304 is the only stored misfire code (or if there are P0300, P0301–P0308 codes as well). Note any freeze-frame data (RPM, load, fuel trim, etc.).
• Check misfire counters and live data: Cylinder 4 misfire counter, cylinder fuel trims, misfire activity under various RPM/loads.

Step 2 — Inspect the mechanical and ignition basics on cylinder 4

• Spark plug:
  • Remove the cylinder 4 spark plug. Inspect for fouling (oil, fuel, carbon), correct gap, or damage.
  • Measure spark plug gap and compare to OEM specification. Replace if worn or fouled.
• Ignition coil/coil-on-plug:
  • Inspect the coil boot for cracks or corrosion. Check electrical connector for corrosion or loose fit.
  • If you have a known-good coil, swap coils between cylinder 4 and another cylinder (e.g., 1 or 2) to see if the misfire follows the coil.
• If the spark plug or coil appears suspect, replace as a first test.

Step 3 — Spark plug/coil swap test (isolate coil vs plug)

• Swap the cylinder 4 coil with the coil from another cylinder. Clear codes and test drive.
  • If P0304 follows the coil to the new cylinder, the coil is faulty.
  • If P0304 remains on cylinder 4 regardless of coil swap, the problem is not the coil (likely plug, injector, compression, or air/fuel issue on cylinder 4).

Step 4 — Inspect and test the cylinder 4 fuel injector

• Swap the injector from cylinder 4 with another cylinder’s injector (e.g., cylinder 3). Clear codes and test drive.
  • If the misfire transfers to the new cylinder, the injector may be faulty.
  • If the misfire stays on cylinder 4, the injector is likely not the primary fault (though the wiring or PCM drive could still be involved).
• Use a noid light to verify injector signal is being sent by the PCM to injector 4.
• If you have access to a fuel injector balance test or a high-quality scan tool, review injector latency and duty cycle for cylinder 4.

Step 5 — Check fuel pressure and overall fuel system health

• Measure engine fuel rail pressure with a suitable gauge when the engine is running.
• Compare to manufacturer spec for the Ram 1500 engine option (3.6L, 5.7L, or 3.0L EcoDiesel). Inconsistent pressure can cause misfires in one or more cylinders.
• If fuel pressure is low or unstable, diagnose the fuel pump, fuel filter (if applicable), and fuel pressure regulator.

Step 6 — Check for air leaks and vacuum integrity

• Inspect intake manifold gaskets, hoses, and connections around cylinder 4 for leaks.
• Listen for hissing noises at idle and during throttle input or use a leak-detecting spray around suspect areas; if the idle changes when sprayed, you’ve found a vacuum leak.
• Inspect PCV valve and hoses; replace if stuck or clogged.

Step 7 — Compression and mechanical condition

• Perform a compression test on all cylinders, focusing on cylinder 4. Compare with spec and with adjacent cylinders.
• If compression is low on cylinder 4, perform a wet compression test (add a touch of oil to the bore and test again) to differentiate ring/seal wear from valve/seating problems.
• If compression is poor, further diagnosis (leak-down test, head gasket, valve seating) is required and may involve disassembly.

Step 8 — Check for related or contributing features

• Review engine oil consumption and signs of oil fouling if the spark plug shows oil fouling.
• Consider MDS or cylinder deactivation behavior if your Ram is the 5.7L Hemi; misfire can sometimes be influenced by lifter/seal issues when cylinders de-activate.
• Inspect for abnormal exhaust backpressure or EGR issues that could create a misfire condition indirectly.

Step 9 — Re-test after fixes

• Clear codes and run the engine through a few heat-cycle drives (idle, light throttle, moderate acceleration) to see if P0304 returns.
• If another related code appears after the fix (e.g., P0302 or P0306), follow those cylinder-specific misfire diagnostics as needed.

5. RELATED CODES

• P0300: Random/Multiple Cylinder Misfire Detected
• P0301, P0302, P0303, P0305, P0306, P0307, P0308: Misfire in other individual cylinders
• P0171 or P0174: System too lean or rich; may accompany misfires if air/fuel mixture is off
• P0172 or P0173: Rich/lean conditions that could cause misfire symptoms
• Other codes related to ignition or fuel systems (P0351–P0358 for ignition coil circuit problems; P0410 for secondary air; P0440 for evaporative system) if symptoms point elsewhere

6. REPAIR OPTIONS AND COSTS (2025 PRICING)
   Notes:

• Prices vary by region, shop rate, and engine option (3.6L V6, 5.7L Hemi V8, or 3.0L EcoDiesel). The Ram 1500 uses different engine configurations across model years; the following are generalized ranges for common fixes on gasoline engines (3.6L and 5.7L), with caveats for 2025 pricing.
• The “per-cylinder” approach is used where applicable (e.g., replacing a single spark plug or coil). If multiple items are replaced, total costs will be higher.

Spark plug replacement (for cylinder 4; engine types vary: 3.6L V6 typically has 6 plugs; 5.7L V8 has 8 plugs)

• Parts: typically $6–$15 per spark plug (OEM or equivalent)
• Labor: about 0.5–1.0 hours for one cylinder’s plug; if you replace all plugs in the engine, labor increases accordingly
• Estimated total: $120–$280 for replacing a single plug on one cylinder (excluding other components). Replacing all plugs can range from $200–$500, depending on engine type and shop rates.

Ignition coil replacement (cylinder 4)

• Parts: $60–$150 for an OEM or aftermarket coil
• Labor: 0.3–0.8 hours
• Estimated total: $120–$260

Fuel injector (cylinder 4)

• Parts: $60–$180 per injector
• Labor: 0.5–1.0 hours
• Estimated total: $320–$680 if replacing a single injector (more if multiple injectors are replaced or if the fuel rail/pressure needs service)

Fuel system service or fuel pressure issue

• If fuel pressure regulator or pump is failing, part costs can range widely ($200–$800 for pump; regulator $60–$150)
• Labor: 1.0–2.5 hours depending on access

Vacuum/PCV hoses and gaskets

• Parts: $10–$60 depending on hose length and gasket set
• Labor: 0.5–2.0 hours
• Estimated total: $100–$350 depending on complexity

Compression/engine mechanical issues

• Compression test tools are inexpensive if DIY; professional testing and repair can be costly
• If an internal issue (bad cylinder ring, valve seating, head gasket) is found, repair cost can escalate quickly
• Typical serious repair ranges:
  • Head gasket/valve/sealing work: $1,000–$4,000 depending on engine and labor
  • Piston ring/valve repair: $1,500–$4,000 or more depending on engine

PCM/ECU concerns

• If a PCM fault is suspected and requires replacement or reprogramming, parts and labor can range from $350–$1,500 or more, depending on the need for programming and dealer involvement

Recalls/TSBs data

• No recalls found in NHTSA database for this specific issue and model-year range in the provided data.
• If you suspect a factory defect or if you have access to a dealership TSB list beyond the provided data, check with a Dodge dealer or the latest NHTSA/TIS database. Based on the provided data: No recalls found in NHTSA database.

7. DIY vs PROFESSIONAL

• Do-it-yourself (DIY) suitability:
  • Easy/medium: Replacing a single spark plug or ignition coil on Ram 1500 is typically within DIY reach if you have basic hand tools and a torque wrench. You can perform plug/coil swaps to isolate the issue and clear codes.
  • Medium to advanced: Injector testing/replacement, fuel pressure testing, and compression tests require more specialized tools and skills. Live data interpretation is essential for accurate diagnosis.
  • Caution: Some Ram 1500 engines have tight access to some coils, plugs, and the fuel rail; improper torque or injector seating can cause more problems.
• Professional diagnosis:
  • Recommended when the problem persists after basic spark plug and coil swaps, or when compression tests reveal abnormal results.
  • A shop can perform a controlled fuel pressure test, injector balance test, leak-down test, advanced misfire counters, and PCM data analysis.
• Practical approach:
  • Start with basic ignition components (spark plug and coil) on cylinder 4.
  • If no fix, move to injector and fuel system tests.
  • If still unresolved, perform compression tests and broader mechanical checks.
  • Always reset codes after repairs and re-check to verify the misfire is resolved.

8. PREVENTION

• Regular maintenance:
  • Follow the manufacturer’s recommended spark plug replacement intervals for your Ram 1500 engine (3.6L and 3.0L EcoDiesel have their own schedules; 5.7L Hemi has separate timing/product intervals).
  • Use high-quality fuel and keep fuel system clean; consider a fuel system cleaner only as recommended by the vehicle manufacturer.
  • Replace ignition coils when they show signs of wear or upon diagnosis indicating coil failure.
• Air and vacuum integrity:
  • Inspect intake hoses, vacuum lines, and PCV system during routine maintenance and address any cracks, leaks, or disconnections promptly.
• Monitoring and care:
  • If you notice frequent rough idle, misfires, or poor acceleration, address promptly to avoid catalytic converter damage.
  • Keep an eye on fault codes; early intervention often reduces repair costs.
• Use OEM or recommended parts:
  • Using OEM or certified replacement parts can improve reliability and compatibility with Dodge Ram 1500 engines.

Important data note and data limitations

• The provided data indicates no NHTSA owner complaints and no recalls for 2019–2024 Ram 1500 in relation to P0304. This guide is based on general automotive diagnostic knowledge and typical Ram 1500 engine configurations (3.6L V6, 5.7L Hemi, 3.0L EcoDiesel) and common misfire diagnosis principles. Real-world results can vary by engine option, maintenance history, and region.
• If you have access to more specific information (engine type, exact VIN, or a service bulletin database), that can help narrow the diagnosis and cost estimates.