P0304 Code: Dodge Durango (2021-2024) - Causes, Symptoms & Fixes

No recalls found in NHTSA database

According to the provided NHTSA data for the Dodge Durango (2021–2024), there are no owner complaints specifically tied to code P0304, and no recalls listed for this make/model/year. The diagnostic guide below uses general OBD-II and Dodge Durango knowledge to help you diagnose and repair P0304, but note that the data subset is limited and may not capture every real-world issue.

CODE MEANING AND SEVERITY

• What it means: P0304 is a cylinder 4 misfire detected by the engine control module (ECM). The ECM has detected that cylinder 4 did not ignite properly during combustion, causing irregular engine operation.
• Why it matters: A single misfire can be benign for a short period, but persistent misfires reduce performance, raise emissions, risk damage to catalytic converters, and can cause rough running, reduced power, and fuel economy loss.
• Severity (durability of concern): Moderate. If left untreated, misfires can cause excess unburned fuel to enter the exhaust and overheat the catalytic converter. Repeated misfires may also cause downstream sensor troubles and catalytic damage over time.

COMMON CAUSES ON DODGE DURANGO

Note: Durango engines from this era commonly use coil-on-plug ignition with individual ignition coils per cylinder and direct-injectors on many versions (3.6L V6, 5.7L Hemi, etc.). For cylinder 4 specifically, the typical culprits are:

• Faulty spark plug in cylinder 4 (worn, fouled, incorrect gap)
• Faulty ignition coil or coil-on-plug for cylinder 4 (damaged boot, weak spark)
• Faulty or dirty fuel injector for cylinder 4 (sticking injector, clog, or electrical issue)
• Ignition coil boot/wiring harness issue for cylinder 4 (cracked boot, corroded connector, damaged wiring)
• Vacuum leak near cylinder 4 (intake manifold runner gasket or hose leakage)
• Low compression or mechanical issue in cylinder 4 (valve, piston ring, or head gasket) due to wear or damage
• Fuel delivery irregularities (low fuel pressure, intermittent fuel rail issue) affecting one cylinder
• Contaminated fuel or fuel adulteration impacting a single cylinder
• Electrical/electronic fault persisting (rare but possible): ECM input/output issue related to cylinder 4 circuitry

SYMPTOMS

• Check Engine Light (CEL) illumination with a P0304 code
• Rough idle or engine stumble at idle
• Noticeable loss of power or hesitations during acceleration
• Decreased fuel economy
• Vibration or shuddering, especially under load or at low RPM
• Misfire may be intermittent or persistent
• In some cases, other P03xx codes (P0301–P0306) may appear if multiple cylinders misfire or the misfire moves between cylinders

DIAGNOSTIC STEPS

A careful, methodical approach helps avoid unnecessary parts replacement. Use an OBD-II scanner and basic hand tools.

A. Confirm and collect data

• Read P0304 with scanner, note freeze-frame data: engine RPM, load, vehicle speed, engine temperature, fuel trim, etc.
• Check for related codes (P0300 generic random/multiple misfire; other P0301–P0306 cylinder-specific codes) and pending codes.
• Observe misfire counters if the scanner provides them.

B. Visual and quick checks

• Inspect the spark plug for cylinder 4: fouling, oil on the electrode, heavy wear, or improper gap.
• Inspect the ignition coil for cylinder 4: damaged boot, cracking, or signs of wear; check coil connection for corrosion or loose fit.
• Check the cylinder 4 fuel injector electrical connector and wiring for damage or corrosion.
• Look for obvious vacuum leaks around the intake manifold runner for cylinder 4.

C. Spark and ignition checks

• Spark plug replacement/test: If the plug looks worn or fouled, replace it. Use the correct heat range and gap as per the owner's manual.
• Coil check: If coil 4 shows signs of weakness or if you have a known defective coil in your fleet, swap the coil from cylinder 4 with another cylinder (e.g., cylinder 2) and clear codes. If the misfire code follows the coil, the coil is faulty.
• Spark plug and coil swap test method:
  • Swap coil (or complete coil-on-plug assembly) from cylinder 4 to another cylinder and drive briefly to see if the misfire code moves. If P030X moves with the coil, the coil is at fault.

D. Fuel injector and fuel system checks

• Noid light test: Confirm that the injector 4 is being driven when commanded (noid light on the injector circuit).
• Injector resistance/coil test: Compare injector 4 resistance to spec (specs vary by model; consult service data). A drastically different resistance or open/short circuit indicates a faulty injector.
• Listen or measure flow: A technician can listen with a mechanic’s stethoscope or use a balance test to determine injector operation. A stuck injector can cause a cylinder to misfire.
• Fuel pressure test: Verify that rail pressure is within specification; a failing fuel pump or pressure regulator can create misfires when one cylinder runs lean/fuel-starved.

E. Mechanical checks

• Compression test or leak-down test for cylinder 4: Low compression or a leak-down indication points to mechanical problems (burned valve, damaged piston, or head gasket issue).
• If compression is normal, focus on other components (spark/ignition/injector/fuel pressure).

F. After testing

• If a faulty component is found (plug, coil, injector, harness), replace and re-test.
• Clear codes and run a controlled road/diagnostic drive to verify the misfire is resolved.
• If no fault is found after thorough testing, consider ECU/software issues or less common causes; consult a dealer if needed.

G. Special notes

• Always perform a complete misfire diagnostic workflow rather than replacing multiple parts at random. Misfires can be caused by multiple reasons, and sometimes more than one issue exists.
• If you replace parts (e.g., spark plug and coil) on cylinder 4, it’s often prudent to consider replacing the other cylinder’s wear-prone parts at the same time to maintain even performance.

RELATED CODES

• P0300 – Random/Multiple Cylinder Misfire
• P0301 – Cylinder 1 misfire
• P0302 – Cylinder 2 misfire
• P0303 – Cylinder 3 misfire
• P0305 – Cylinder 5 misfire
• P0306 – Cylinder 6 misfire
• P0304 – Cylinder 4 misfire (current focus)

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices vary by region, shop type (dealer vs. independent), and engine configuration (3.6L V6, 5.7L Hemi, etc.). TheDurango commonly uses six individual cylinders; cylinder 4 is not treated any differently in parts availability, but access may vary by engine layout.

• Spark plug replacement (cylinder 4 only)

  • Parts: roughly $5–$25
  • Labor: $60–$140
  • Total: $65–$165
  • All-six-plug replacement (recommended for reliability)
  • Parts: $30–$120
  • Labor: $150–$300
  • Total: $180–$420

• Ignition coil for cylinder 4 (coil-on-plug)

  • Parts: $60–$160
  • Labor: $40–$100
  • Total: $100–$260

• Fuel injector for cylinder 4

  • Parts: $150–$350
  • Labor: $100–$200
  • Total: $250–$550
  • Note: If replacing multiple injectors or cleaning the entire fuel rail, costs rise.

• Fuel system cleaning or injector cleaning (optional diagnostic step)

  • Cost: $80–$150

• Vacuum leak repair (e.g., intake runner gasket, hoses)

  • Parts: $20–$150
  • Labor: $80–$250
  • Total: $100–$400

• Compression testing or leak-down testing

  • Labor: $100–$250 (if done by a shop; some shops include it with other diagnostics)

• Mechanical repairs for compression issues (valve, piston, head gasket)

  • Very variable; typical engine-internal repairs can range from $1,000 to $4,000 or more depending on severity and parts required.

• ECU/PCM software update or reprogramming

  • Dealer price range: $60–$150 (varies by region and availability of updates)

Important notes on pricing:

• These are ballpark estimates for 2025. Actual costs depend on parts brand (OEM vs aftermarket), labor rate in your area, and whether you choose dealership or independent shops.
• If multiple cylinders misfire or if the misfire is persistent and mechanical, costs may go higher due to additional testing or major components replacement.

DIY VS PROFESSIONAL

• DIY suitability: Moderate to challenging for a competent home mechanic, especially if you must access rear bank spark plugs or work around tight engine bays. Tools you may need include a spark plug socket with extension, torque wrench, standard hand tools, a noid light, basic multimeter, and possibly a compression tester. Access to cylinder 4 may require moving or removing components (e.g., intake plenums or coil packs). If you’re comfortable with automotive electrical diagnostics and basic engine work, you can save on labor by tackling spark plug and coil replacement or swapping tests.
• When to go pro:
  • If you’re unsure about ignition/ injector electrical tests (noid light, injector resistance, coil primary/secondary resistance).
  • If you suspect mechanical issues (compression problems) or engine internal damage.
  • If access is difficult due to your engine variant (some Durango engines place rear-bank plugs in tight areas).
  • If you lack proper tools or risk of damaging components is high.
• Safety: Always disconnect the battery when performing electrical work on ignition components, and follow proper torque specs to avoid damaging the spark plugs or cylinder head.

PREVENTION

• Regular maintenance at the manufacturer-recommended intervals:
  • Replace spark plugs at the recommended interval using OEM-spec parts; even if a single plug seems fine, mismatched wear can contribute to misfires.
  • Use high-quality fuel and maintain a clean fuel system; consider a fuel system cleaner if recommended by your dealer (not a substitute for failed injectors).
  • Replace ignition coils and related wiring if there are signs of aging, cracking, or poor connections.
  • Keep intake and vacuum lines in good condition; fix leaks promptly.
  • Address any rough idle or under-acceleration issues promptly before they worsen.
  • If you know you have a history of injector or coil problems in your vehicle, consider proactive testing where appropriate (e.g., injector resistance checks during service).
• Monitoring: If you notice continuing rough idle, power loss, or a CEL, diagnose promptly to avoid catalyst damage and excessive emissions.

Important data note

• The data provided for this guide shows no NHTSA owner complaints and no recalls for P0304 on the 2021–2024 Dodge Durango in the dataset. This means the diagnostic guide relies on general OBD-II and Dodge engine knowledge, not on a dataset of reported Durango P0304 failures. Real-world experience with a particular vehicle may differ, and local shop data or a dealer service bulletin could provide additional insights not captured here.