P0304 Code: Nissan Sentra (2020-2024) - Causes, Symptoms & Fixes

P0304 Diagnostic Guide for 2020-2024 Nissan Sentra (P0304 = Cylinder 4 Misfire)

Note on data limitations

• Real-NHTSA data for this exact make/model/year/issue: No owner complaints found.
• Official recalls: No recalls found in NHTSA database.
• Because there are no documented complaints or recalls in the provided data, this guide relies on general automotive knowledge for the Nissan Sentra 2020–2024 and standard OBD-II misfire diagnostic practices. Use this as a structured starting point, not a guarantee of a specific factory fix.

CODE MEANING AND SEVERITY

• What P0304 means: The powertrain control module (PCM) has detected a misfire in cylinder 4. This is reported as a cylinder-specific misfire code.
• Severity:
  • Moderate to high risk if left untreated: repeated misfires can damage the catalytic converter, increase exhaust emissions, reduce engine performance, and potentially cause ignition-related engine damage over time.
  • You may notice rough idle, reduced acceleration or drivability issues, and a flashing or solid check engine light depending on the persistence and severity of the misfire.

COMMON CAUSES ON NISSAN SENTRA (2020–2024)

Typical sources for a cylinder 4 misfire on modern Sentra models:

• Ignition system
  • Faulty spark plug in cylinder 4 (worn, fouled, or misgapped)
  • Faulty ignition coil for cylinder 4 (coil-on-plug pack or coil failure)
  • Damaged ignition coil boot or wiring to coil
• Fuel delivery
  • Clogged or leaking fuel injector for cylinder 4
  • Low fuel pressure or faulty fuel pump affecting cylinder 4’s fuel delivery
  • Dirty or contaminated fuel
• Air and vacuum
  • Vacuum leaks around intake manifold or PCV system
  • Dirty or faulty mass air flow (MAF) sensor or intake air leaks altering air/fuel trim
• Engine/mechanical
  • Low compression in cylinder 4 (ring/seal/valve issue)
  • Damaged or bent valve or piston issues in cylinder 4 (less common)
• Sensors/ECU related
  • Wiring harness or PCM connection issues
  • Faulty related sensors causing misfire patterns (e.g., O2 sensor or crank sensor fault can trigger misfire codes indirectly)
• Miscellaneous
  • Dirty or degraded fuel injectors or injector seal leaks
  • Exhaust leaks before the O2 sensors that mimic or contribute to misfire symptoms

SYMPTOMS

• Check engine light (MIL) illuminated or flashing, depending on persistence
• Rough idle or vibration at idle, especially when parked or idling
• Hesitation, stumbling, or reduced power during acceleration
• Poor fuel economy or noticeable engine shudder during acceleration
• Occasional misfire indicators in data stream (via scan tool): cylinder 4 misfire counter
• Possible secondary symptoms if catalyst is affected: elevated exhaust temperature or smell, but typically more noticeable if misfires are frequent

DIAGNOSTIC STEPS

Follow a structured approach to confirm P0304 and identify root cause. Use a scan tool to read DTCs, freeze-frame data, and live misfire counters.

Step A – Confirm the DTC and gather data

• Confirm P0304 is current and not a historical, pending, or intermittent code.
• Check for related codes: P0300 (random/multiple misfires) or P0301, P0302, P0303 (cylinder-specific). Also note any fuel trim (short-term and long-term) and fuel pressure reading if supported.
• Review freeze-frame data for RPM, load, temperature, gear, etc., around the misfire event.

Step B – Visual and basic mechanical inspection

• Inspect cylinder 4 spark plug: condition, gap, electrode wear, fouling (oil, fuel), and signs of spark plug detonation. Replace if worn or fouled.
• Inspect cylinder 4 ignition coil (coil pack or coil-on-plug boot): look for cracks, overheating discoloration, oil contamination, and test plug-in connectors for corrosion or loose pins.
• Check wiring harness and connectors to the cylinder 4 coil and spark plug for damage or looseness.
• Inspect intake manifold area, vacuum hoses, and PCV system for cracks or leaks near cylinder 4.

Step C – Isolate ignition vs fuel vs compression

• Ignition test (swap test):
  • If you have coil-on-plug for cylinder 4, swap the cylinder 4 coil with another cylinder (e.g., cylinder 1). Clear codes, run engine, and see if the misfire follows the coil to the new cylinder. If P0301 or another cylinder code appears after swap, the coil is likely faulty.
  • If misfire stays on cylinder 4 after swapping coils, the problem is more likely not the coil.
• Spark plug test/replace:
  • If the spark plug in cylinder 4 is fouled or worn, replace all spark plugs (recommended to replace all four for even performance and cost efficiency). Use OEM gap specification.
• Fuel delivery test:
  • Listen for injector operation on cylinder 4 with a mechanic’s stethoscope or use a noid light to verify injector signal if applicable.
  • Check fuel pressure with a gauge to ensure it meets what Nissan specifies for the 2.0L engine (note: exact spec varies by model/engine; consult service data).
  • Consider injector cleaning if suspected clogging; replace if cleaning doesn’t resolve issue.
• Vacuum/air system check:
  • Perform a spark test with vacuum on the intake side to identify leaks. Smoke test can be helpful for locating vacuum leaks that can cause misfires.
• Compression test:
  • Perform a compression test on all cylinders, including cylinder 4. Note readings and compare to factory spec and each other. Low compression on cylinder 4 indicates a mechanical issue (valve, piston, rings, or head gasket concern) requiring further diagnosis or repair.
• Sensor and wiring checks:
  • Inspect relevant wiring to O2 sensor, MAF, MAP, and crank/cam sensors. Although P0304 is primarily a misfire, a faulty sensor can contribute to misfire conditions by causing improper air-fuel mixture or ignition timing.

Step D – If ignition, fuel delivery, and compression are ruled out

• Verify PCV/heater hoses and any intake leaks not previously found.
• Review for PCM/software updates or service bulletins. In this data set, there are no recalls listed; there are no specific TSBs cited here. If you have access to dealership service literature or a broader data source, check for any engine misfire-related TSBs for the 2020–2024 Sentra.
• After repairs, re-scan and drive under varying loads to confirm the misfire is resolved and the Live Data shows stable misfire counters.

Step E – Final verification

• Clear codes after repair and perform a test drive that includes idle, light, and heavier acceleration to confirm permanent fix.
• If misfire returns, re-check the suspected system area and consider professional diagnosis (engine mechanical issues or PCM faults may need more specialized testing).

RELATED CODES

• P0300: Random/Multiple Cylinder Misfire Detected
• P0301: Cylinder 1 Misfire
• P0302: Cylinder 2 Misfire
• P0303: Cylinder 3 Misfire
• P0305–P0308: Cylinder 5–8 Misfire (if applicable on other engines; Sentra 4-cyl typically uses P0301–P0304)
• Other related codes that can accompany misfire scenarios:
  • P0130–P0133: O2 sensor issues
  • P0171/P0174: System too rich/too lean (fuel trim issues)
  • P0172/P0175: Bank 1/Bank 2 system too rich/lean (if engine has more cylinders or specific sensor data)
  • P030x may appear with PCM or sensor-related faults if wiring or grounding issues are present
  • P0304 does not automatically imply a single root cause; misfire codes often require stepwise testing to identify ignition, fuel, vacuum, or mechanical faults

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices are approximate ranges in USD and will vary by region, labor rates, and whether you use OEM, aftermarket, or remanufactured parts. All numbers assume typical labor shop rates in the 80–180 USD/hour range.

• Spark plug replacement (cylinder 4 only, and typically all four for best performance)
  • Parts: $4–$28 per plug (OEM or aftermarket)
  • Labor: $30–$100
  • Total: roughly $60–$220 for all four plugs, or $25–$300 if only cylinder 4 plug is done depending on shop policy and hourly rate
• Ignition coil replacement (cylinder 4 coil, coil-on-plug)
  • Parts: $40–$120
  • Labor: $40–$120
  • Total: approximately $80–$240
• Fuel injector service (cylinder 4)
  • Cleaning/flow test: $60–$150
  • Injector replacement (cylinder 4): $150–$400 parts + $50–$150 labor
  • Total: $200–$550
• Fuel system and fuel pump related checks
  • Fuel pressure test: often part of diagnostic charge; not a repair, but if pump/filter is at fault: pump replacement typically $400–$900 (parts + labor)
• Vacuum/PCV systems and hoses
  • Parts: $5–$40
  • Labor: $20–$60
  • Total: $25–$100
• MAF sensor or related sensor cleaning/replacement
  • Sensor cleaning: $0–$20 (do-it-yourself)
  • Replacement: $60–$250 (sensor itself)
  • Labor: $40–$120
• Oxygen sensors (if diagnosed as contributing factor)
  • Parts: $40–$150 each
  • Labor: $60–$150
  • Total: $100–$350 per sensor
• Compression/engine mechanical issue
  • Cylinder 4 compression repair could involve valve seat/valve job or piston ring replacement
  • Parts: highly variable; often $200–$1500+ for parts
  • Labor: $500–$2000+ depending on extent
  • Note: If compression is low due to a mechanical fault, it can be a major repair or engine rebuild; evaluate with a professional.
• ECU/PCM software updates or reflashes
  • Software update or reflashes: $80–$150 (dealer or specialized shop)
  • If a service bulletin or TSB is found later, this could vary

DIY VS PROFESSIONAL

• Do-it-yourself (DIY-friendly if you are comfortable with basic tools and safety):
  • Easy/Moderate tasks: Inspect and replace spark plugs; inspect and swap ignition coil for misfire testing; inspect visible vacuum hoses; clean MAF sensor, replace PCV valve; basic fuel rail inspections with proper safety.
  • Moderate tasks: Testing fuel pressure, injector noid testing, compression testing, and conducting a controlled coil swap test; requires tools and safety awareness.
  • Important caveats: Dealing with ignition components (high voltage) or fuel system pressure requires caution; disconnect battery before servicing electrical components; ensure you have proper tools, torque specs, and procedure.
• Professional diagnosis and repair:
  • Recommended if: misfire persists after basic checks, unknown cause remains after ignition/fuel/air checks, compression test shows abnormal results, or you suspect mechanical damage (valve, piston, ring) or PCM issues.
  • Pros: Proper diagnostics, access to factory service data, accurate fuel trim analysis, precise injector testing, and guaranteed repair.

PREVENTION

• Maintain ignition system health
  • Replace spark plugs at Nissan-recommended intervals (often every 60,000–100,000 miles for many modern engines, check your owner’s manual for exact interval)
  • Inspect ignition coils and coil boot/good connection; replace any failing coil promptly
• Maintain fuel system integrity
  • Use high-quality fuel and keep fuel system clean
  • Replace fuel filter as per schedule (if applicable to your engine; some Sentras may not have a separate fuel filter in certain markets)
• Protect intake and vacuum systems
  • Inspect and replace cracked vacuum hoses and PCV components; perform a smoke test if you suspect leaks
  • Keep air intake clean; replace air filter as recommended
• Maintain sensors and air/fuel management
  • Clean or replace dirty MAF sensors as needed; ensure proper air intake leaks are addressed
  • Regularly inspect O2 sensors and consider replacement per warranty or symptoms
• Regular maintenance schedule
  • Follow Nissan’s maintenance plan for spark plugs, coils, fuel system checks, and engine performance diagnostics
• Driving habits
  • Avoid prolonged periods with a misfiring cylinder; address rough idling or hesitation promptly to avoid catalyst damage
• Diagnostics readiness
  • If you notice intermittent misfires, keep a log of when it occurs (idle, cold start, acceleration) to aid diagnosis

Important data transparency note

• This guide is based on the provided dataset, which indicates no NHTSA owner complaints and no recalls for P0304 on 2020–2024 Nissan Sentra. No official TSBs or recalls are cited in the data above. Real-world service information may include additional TSBs or dealership notes not reflected here. Use this guide as a diagnostic framework, and verify against up-to-date service information for your vehicle.