P0304: Fallo de combustión detectado en el cilindro 4
El código de diagnóstico de fallas (DTC) P0304 indica que el módulo de control del motor (ECM/PCM) ha detectado una pérdida total de combustión o una condición recurrente de fallo de combustión localizada específicamente en el cilindro 4. En un motor diésel de riel común -el cual carece de sistema de encendido por chispa-, la detección de fallos se calcula exclusivamente a través del sensor de posición del cigüeñal (CKP) de alta resolución, el cual monitorea variaciones de submicrosegundos en la velocidad angular del cigüeñal. Cuando la carrera de trabajo del cilindro 4 (30° - 90° después del punto muerto superior / ATDC) genera una caída por desaceleración rotacional en lugar de un incremento de aceleración que supere los umbrales calibrados (típicamente >2.0% de los eventos de combustión monitoreados), se almacena el código P0304.
🚗 Seguridad operativa, presupuesto estimado y verificación
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🚦 Seguridad de conducción y riesgo mecánico
Evaluación mecánica inmediata y necesidad de grúaFallo de combustión en cilindro 4 - Alto riesgo térmico en el cilindro posterior
El cilindro 4 (el más próximo al cortafuegos en la mayoría de los motores de 4 cilindros en línea) presenta fallos de combustión. Debido a que los cilindros posteriores operan a mayores temperaturas por un flujo de aire reducido, la conducción prolongada con una mezcla pobre o rica genera un riesgo severo de estrés térmico localizado y daños en la junta de culata.
PELIGROS MECÁNICOS SI CONTINÚA CONDUCIENDO:Daño localizado por puntos calientes en la culata, quemado de válvulas de escape debido al combustible sin quemar que arde en la carrera de escape y saturación súbita de hollín en el filtro de partículas diésel (DPF).Síntomas observables en el vehículo:- Severe engine vibration and rhythmic shudder noticeable through steering wheel and floorpan
- Deep engine chugging sound and distinct loss of acceleration under any uphill load
- Exhaust tailpipe emits greyish smoke with pungent raw unburnt diesel odor
- Cruise control disabled and transmission shifting erratically
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💰 Presupuesto típico de taller
Niveles de costo esperados para repuestos y mano de obraMantenimiento menor / Filtro$35 - $100: Ajuste de pines del conector del inyector, reemplazo del filtro de combustible y verificación de resistencia en bujías de precalentamiento.Limpieza de sensor, cambio de filtro de combustible, revisión de fusibles o conectores.
Cambio de válvula / Sensor$220 - $480: Sustitución por un inyector remanufacturado de calidad con arandela de cobre y perno de fijación nuevos.Sustitución de componente individual (válvula reguladora, unidad dosificadora o inyector reconstruido).
Reparación mayor / Bomba e inyectores$1,100 - $2,500+: Inyector nuevo original de fábrica, tubería de alta presión y descarbonización con cáscara de nuez (walnut blasting) del múltiple de admisión si está obstruido por carbonilla.Revisión de bomba de alta presión, juego de inyectores nuevos o sustitución del conjunto DPF.
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🧰 Verificaciones visuales rápidas en garaje
Chequeo de 5 minutos sin herramientas antes de ir al taller1Revisar el cableado del cilindro 4 cerca del cortafuegos: Inspeccionar el área donde el mazo de cables del motor discurre próximo a las tuberías calientes de escape o del sistema EGR.2Oler los gases de escape: Un olor penetrante a diésel crudo indica que el combustible se está pulverizando pero no se produce la autoinflamación correctamente.3Inspeccionar el tapón de llenado de aceite: La presencia de una emulsión blanquecina densa (tipo mayonesa) indica contaminación cruzada de refrigerante y aceite por fallo en la junta de culata, descartando un problema exclusivo del inyector. - 04
🛡️ Protección ante diagnósticos erróneos en taller
Preguntas técnicas exactas para evitar sustituciones de piezas innecesarias"Indique al taller: 'Por favor, realicen una prueba de resistencia eléctrica (ohmios) en el solenoide del inyector del cilindro 4 (rango especificado: 0.2 - 0.5 ohmios) antes de diagnosticar una avería mecánica interna.'"
"Indique al taller: 'Asegúrense de registrar e ingresar el nuevo código de calibración IMA/IQA de 6/7/8 caracteres en la unidad de control del motor.'"
Nota técnica: Haga estas preguntas técnicas a su mecánico antes de autorizar presupuestos caros:
Triaje de taller en 30 segundos
- Violent engine shaking, severe vibration, and rhythmic thumping at idle (running distinctly on 3 cylinders)
- Flashing or steady Check Engine Light (MIL) on dashboard, accompanied by flashing glow plug light and ESP/traction warning
- Massive loss of engine power, sluggish throttle response, and inability to accelerate up highway gradients
- Completely failed Cylinder 4 fuel injector (blown solenoid coil, seized command piston, or cracked nozzle needle)
- Low mechanical cylinder compression on Cylinder 4 caused by a burnt exhaust valve, broken rocker arm, or holed piston (runs hottest near firewall)
- Burned-out or heavily carbon-crusted Cylinder 4 glow plug preventing compression ignition during cold ambient starts
Connect scan tool live telemetry: compare Target Fuel Rail Pressure vs Actual Rail Pressure and log metering valve command PWM duty cycle during idle and road load.
Expensive Diagnostic Pitfall & Technical Reality
P0304 means Cylinder 4 has suffered piston ring failure or burned exhaust valves, requiring cylinder head removal ($2,000 - $3,800).
Cylinder 4 sits closest to the firewall where heat dissipation is poorest, making its injector harness wiring and sealing components prone to premature thermal aging. In over 80% of verified cases, mechanical compression is normal. The misfire is almost always caused by an injector with a clogged nozzle spray hole from carbon coking, a degraded harness connector whose spring leaves have widened under heat, or high internal valve backleak.
Unnecessary engine rebuild or full injector set replacement ($2,400+) vs ultrasonic cleaning of the nozzle ($0) or repairing the $15 harness pigtail connector, saving over $2,200.
Motores y plataformas de inyección más afectados
Este código de error afecta principalmente a las siguientes plataformas diésel common rail. Consulte su familia de motores para ver fallos típicos y referencias de piezas:
Ford / PSA 1.6 TDCi / HDi (DV6ATED4 / DV6TED4)
Bosch CRI2 Solenoid Common RailSíntoma típico: Distinct chuffing exhaust sound from rear of engine, tar crust encrusting injector 4, and P0304 stored.
Fallo típico de fábrica: Crushed copper sealing washer blow-by due to injector hold-down clamp stud loosening under thermal cycling.
0445110239 (Injector) / PSA 198299 / 198185 (Seal Kit)Mercedes-Benz 2.1 CDI OM651 (Sprinter, C220 CDI, E220 CDI)
Delphi CRD2 / CRD3 Common RailSíntoma típico: Severe cab vibration at idle, engine enters Limp-Home Mode, and Cylinder 4 smooth running value pegged in Xentry.
Fallo típico de fábrica: Delphi injector control valve internal micro-grooving dumping high return volume back to tank on rear cylinder.
A6510704987 / Delphi 28342997 / 28348371Volkswagen / Audi 2.0 TDI EA189 / EA288 (Golf, Passat, Tiguan, A3, A4)
Bosch CRI2.2 Solenoid / CRI3 PiezoSíntoma típico: Flashing glow plug spiral indicator on instrument cluster accompanied by harsh cold-idle clatter on Cylinder 4.
Fallo típico de fábrica: Cylinder 4 injector control valve seat erosion or piezo stack moisture penetration causing delivery collapse.
0445110369 / 03L130277B (Bosch CRI2.2 Injector)BMW 2.0d N47 / B47 (120d, 320d, 520d, X1, X3)
Bosch CRI3 Piezo / Solenoid Common RailSíntoma típico: Rough idle when cold, drivetrain malfunction message in iDrive, and intermittent P0304 code stored.
Fallo típico de fábrica: High thermal stress on rear cylinder causing injector 4 piezo crystal micro-cracking and electrical leakage to ground.
0445115077 / 0445116001 / BMW 13537796042Cylinder Balance & Injector Deviation Guide
Common rail diesel cylinder balance & smooth running diagnostic guide. Balance rates, mg/stroke deviation, P0263 misfire, compression vs injector test.
Circuito de control y lógica del actuador
1. Dynamic In-Demand Fuel Metering
Diesel compression ignition requires three mandatory physical conditions: high cylinder compression (>22 bar producing air temperatures above 500°C), precise atomization of high-pressure diesel fuel (>250 bar cranking, >1400 bar running), and exact injection timing. The ECM tracks the rotational speed of the flywheel tone ring (60-2 or 36-2). When Cylinder 4 fires correctly, crankshaft rotational speed accelerates sharply. If combustion fails completely (zero heat release), the drag of compressing air causes the crankshaft to slow down rapidly during Cylinder 4's segment, triggering the misfire monitor.
2. Closed-Loop PID Deviation Monitoring
The ECM evaluates misfire data across two independent severity windows: 1. Catalyst / DPF Damaging Window (200 engine revolutions): If the misfire rate is severe enough to allow raw fuel into the exhaust (causing DPF melting), the Check Engine Light flashes violently. 2. Emissions Compliance Window (1,000 engine revolutions): If misfire percentage exceeds 2.0% to 3.0%, a continuous DTC P0304 is logged. The ECM attempts initial compensation by adding fuel via Smooth Running Control (SRC); if the cylinder fails to respond, the ECM cuts fuel to Cylinder 4 to prevent catalytic converter destruction.
3. Diagnostic Trap: Normally Open (NO) vs Normally Closed (NC) Valves
Misfire (P0304) vs Balance Contribution (P0272) Diagnostic Rule: P0272 indicates PARTIAL combustion (the cylinder is running but producing less torque due to coked nozzle holes or minor leakage). P0304 indicates a COMPLETE DEAD MISS: Cylinder 4 has suffered complete combustion failure. In diesel workshops, a dead miss on Cylinder 4 is frequently caused by its location at the rear of the cylinder head against the firewall: it runs with the highest thermal heat soak, leading to accelerated injector nozzle varnish baking, valve guide wear, and head gasket fire ring fatigue.
Valores físicos eléctricos e hidráulicos
Protocolo de Diagnóstico de Taller Paso a Paso
Injector Cross-Swap Physical Verification (Hardware vs Mechanics)
Remove the Cylinder 4 fuel injector and swap it with Cylinder 1 (using brand-new annealed copper crush washers). Reprogram the respective IMA/QR calibration codes into the ECM via scan tool. Clear trouble codes and start the engine. If the misfire code moves from P0304 to P0301 (Cylinder 1), the injector has an internal mechanical/hydraulic failure: replace it. If the misfire remains stubbornly on Cylinder 4 (P0304), the problem is 100% mechanical (compression/valvetrain) or wiring.
Electronic Relative Compression & Mechanical Gauge Test
Execute an electronic 'Relative Compression Test' via diagnostic scan tool, which monitors starter current draw and crankshaft angular speed across each cylinder's compression stroke. If Cylinder 4 shows <85% relative compression, remove the Cylinder 4 glow plug and thread in a physical diesel mechanical compression gauge. Crank engine: compression must exceed 22 bar (320 psi) with <3 bar variance to companion cylinders. A reading below 18 bar confirms blown piston rings, burnt valves, or a blown head gasket.
Individual Injector Backleak (Return Flow) Measurement
Disconnect the low-pressure fuel return lines from all injectors. Attach graduated transparent test tubes to the return nipples. Crank the engine for 15 seconds (or run at warm idle for 2 minutes). A healthy injector returns less than 20-25 mL at idle. If Cylinder 4 returns excessive fuel (>40 mL) or fills the bottle instantly during cranking, its internal control valve has collapsed, dumping rail pressure and preventing the needle from lifting.
Injector Solenoid Coil Resistance & 250V Megohmmeter Test
Disconnect the Cylinder 4 injector harness. Using a precision digital multimeter on the 200 Ω scale, measure coil resistance: solenoid injectors must measure 0.20 Ω to 0.45 Ω @ 20°C; piezo injectors must measure 180 kΩ to 220 kΩ. Next, test insulation resistance to the metal body with an automotive insulation tester set to 250V/500V test voltage (must exceed >10 MΩ). A low reading confirms high-voltage dielectric breakdown arcing into the cylinder head.
Glow Plug Resistance & Power Feed Audit (Cold Start Misfires)
If the P0304 misfire occurs exclusively during the first 3 to 5 minutes following a cold start, disconnect the Cylinder 4 glow plug lead. Measure resistance between the glow plug center terminal and engine cylinder block ground. A healthy glow plug measures 0.4 Ω to 1.2 Ω. An open circuit (infinite resistance / OL) confirms a burned-out glow plug that leaves Cylinder 4 too cold to ignite diesel.
Cylinder 4 Valvetrain & Camshaft Lobe Inspection
Remove the engine valve/camshaft cover. Visually inspect the intake and exhaust camshaft lobes and roller rocker arms for Cylinder 4. Look for worn, flattened camshaft lobes (very common on high-mileage VAG TDI and Ford engines) or collapsed hydraulic lash adjusters. A flattened intake cam lobe prevents the intake valves from opening fully, starving the cylinder of oxygen.
Reparación de hardware y lista de piezas BOM
Cylinder 4 Fuel Injection & Combustion Chamber Sealing Interface
0 445 110 369 / 0 445 116 059
High-speed electro-hydraulic fuel injector with calibrated pilot/main injection metering
F 00V C17 503 / OEM Copper Crush Washer
Gas-tight sealing ring between injector nozzle shoulder and cylinder head bore seat (prevents combustion blowby)
1 928 498 056 / Tyco Junior Timer 2-Way
Provides positive terminal spring tension to withstand 150V injection pulse vibrations
Calculadora interactiva de tolerancias Common Rail
Componentes de inyección asociados
Las siguientes bombas de combustible e inyectores common rail originales están verificados para motores con el código P0304. Verifique las presiones de trabajo antes del reemplazo:
0445115077BOSCH
BOSCH 0445115077 Piezo Common Rail Injector for BMW 330d / 530d / X5 3.0d M57N2
View Technical Specs & Fitment →0445110239BOSCH
0445110239 Injector: PSA 1.6 HDi Ford 1.6 TDCi Specs
View Technical Specs & Fitment →0445110369BOSCH
0445110369 Injector: VW 2.0 TDI EA189 CFFB CFHC Specs
View Technical Specs & Fitment →095000-5880Denso
095000-5880 Denso Toyota 2KD-FTV Injector: 23670-30050 Data
View Technical Specs & Fitment →28337917Delphi
28337917 Delphi Bobcat D24 Injector: 7030364 Specs & Data
View Technical Specs & Fitment →095000-8340Denso
095000-8340 Denso Mitsubishi 4D56 HP Injector: 1465A367 Data
View Technical Specs & Fitment →Reinicio de adaptación de bomba y ciclo de rodaje
Following replacement of the Cylinder 4 fuel injector, glow plug, or cylinder head servicing, execute the adaptation routine:
1. Enter the new 6-to-30 digit alphanumeric calibration code (IMA/QR code) stamped on the top of the new Cylinder 4 injector into the ECM via scan tool.
2. Clear all stored diagnostic trouble codes and confirm engine coolant temperature is above 75°C (167°F).
3. Access scan tool 'Engine Control Module' -> 'Special Functions' -> select 'Reset Cylinder Balance / Smooth Running Values'.
4. Start the engine and allow it to idle undisturbed in park/neutral for 5 minutes without touching any pedals, allowing the ECM to build initial torque offsets.
5. Accelerate vehicle smoothly in 4th gear to 80 km/h (2200 RPM), then release throttle completely to coast down in gear to 35 km/h (minimum 8s overrun).
6. Repeat this acceleration and coast-down sequence 5 times. Return to workshop and confirm Cylinder 4 misfire counter remains at absolute zero.
Diagnóstico diferencial y códigos relacionados
Random or Multiple Cylinder Misfire Detected
Multi-cylinder misfire code triggered when systemic issues (air in fuel, bad fuel, low rail pressure) cause misfiring across multiple cylinders.
Cylinder 4 Contribution/Balance Fault
Milder predecessor fault indicating Cylinder 4 is producing degraded torque; if contribution degrades further into complete flameout, P0304 triggers.
Injector Circuit/Open - Cylinder 4
Electrical circuit fault code on Cylinder 4; if an injector wiring open/short develops, P0204 will trigger alongside or override P0304.
Casos reales de taller
2016 Mercedes-Benz Sprinter 316 CDI (OM651)(210,000 km)
Preguntas técnicas frecuentes
¿Qué significa el código de fallo P0304?
El código de diagnóstico de fallas (DTC) P0304 indica que el módulo de control del motor (ECM/PCM) ha detectado una pérdida total de combustión o una condición recurrente de fallo de combustión localizada específicamente en el cilindro 4. En un motor diésel de riel común -el cual carece de sistema de encendido por chispa-, la detección de fallos se calcula exclusivamente a través del sensor de posición del cigüeñal (CKP) de alta resolución, el cual monitorea variaciones de submicrosegundos en la velocidad angular del cigüeñal. Cuando la carrera de trabajo del cilindro 4 (30° - 90° después del punto muerto superior / ATDC) genera una caída por desaceleración rotacional en lugar de un incremento de aceleración que supere los umbrales calibrados (típicamente >2.0% de los eventos de combustión monitoreados), se almacena el código P0304.
¿Cuáles son los síntomas más comunes de P0304?
Violent engine shaking, severe vibration, and rhythmic thumping at idle (running distinctly on 3 cylinders), Flashing or steady Check Engine Light (MIL) on dashboard, accompanied by flashing glow plug light and ESP/traction warning, Massive loss of engine power, sluggish throttle response, and inability to accelerate up highway gradients, Dense clouds of white or blue-grey exhaust smoke on cold start (raw unburned atomized diesel fuel vapor), Overwhelming raw diesel exhaust odor noticeable around the vehicle and through cabin air vents, Scan tool live data shows Cylinder 4 misfire counter incrementing rapidly (>50 counts per 1000 revolutions).
¿Qué causa P0304 en un motor diésel?
Completely failed Cylinder 4 fuel injector (blown solenoid coil, seized command piston, or cracked nozzle needle); Low mechanical cylinder compression on Cylinder 4 caused by a burnt exhaust valve, broken rocker arm, or holed piston (runs hottest near firewall); Burned-out or heavily carbon-crusted Cylinder 4 glow plug preventing compression ignition during cold ambient starts; Broken, corroded, or shorted wiring harness wire between the ECM and the Cylinder 4 fuel injector connector; Internal low-side power MOSFET driver transistor failure for Cylinder 4 inside the Engine Control Module (ECM); Intake valve carbon choking or stuck-shut intake swirl flap starving Cylinder 4 of necessary fresh air charge.
¿Es seguro conducir con el código P0304 activo?
🟡 Precaución: Modo emergencia activo / Acudir a taller
¿Cuánto cuesta reparar el código de avería P0304?
Los costes habituales de reparación para P0304 dependen de la causa raíz identificada en el diagnóstico: Nivel 1 (Mantenimiento menor / DIY): $35 - $100: Ajuste de pines del conector del inyector, reemplazo del filtro de combustible y verificación de resistencia en bujías de precalentamiento. (Limpieza de sensor, cambio de filtro de combustible, revisión de fusibles o conectores.); Nivel 2 (Sustitución de componente): $220 - $480: Sustitución por un inyector remanufacturado de calidad con arandela de cobre y perno de fijación nuevos. (Sustitución de componente individual (válvula reguladora, unidad dosificadora o inyector reconstruido).); Nivel 3 (Subconjunto mayor): $1,100 - $2,500+: Inyector nuevo original de fábrica, tubería de alta presión y descarbonización con cáscara de nuez (walnut blasting) del múltiple de admisión si está obstruido por carbonilla. (Revisión de bomba de alta presión, juego de inyectores nuevos o sustitución del conjunto DPF.). Tarifas de referencia de talleres. Más del 70% de las incidencias se resuelven en Nivel 1 o 2 sin sustituir subconjuntos completos.
Can a bad glow plug cause code P0304 in a diesel engine?
Yes, but specifically during cold starts and the first 3 to 5 minutes of engine warm-up. Unlike gasoline spark plugs which fire continuously, diesel glow plugs only operate during pre-glow and post-glow phases to keep cold cylinder walls warm. If the Cylinder 4 glow plug is burned out, cold compression cannot reach the 500°C auto-ignition temperature of diesel, causing Cylinder 4 to misfire (P0304) and puff white unburned fuel smoke until the cylinder block heats up.
Why does my diesel car misfire on Cylinder 4 under heavy load but idle fine?
At idle, common rail fuel pressure is only 250 to 350 bar, and the injector needs to deliver only a tiny 5 mg micro-pulse. Under full load, rail pressure spikes to 1800+ bar and fuel delivery increases tenfold. If the Cylinder 4 injector has internal control valve wear (excessive backleak) or a partially clogged nozzle, it can deliver enough fuel at low pressure to idle smoothly, but completely fails to deliver the massive volume demanded at 1800 bar, dropping cylinder torque and triggering P0304.
What is the fastest way to confirm whether the Cylinder 4 injector is bad?
The most reliable test is the physical cross-swap. Remove the Cylinder 4 injector and swap it with Cylinder 1 (always install new annealed copper seating washers). Enter the calibration codes into the scan tool and drive the vehicle. If the misfire moves to Cylinder 1 (P0301), you have 100% proven the injector is defective. If the misfire stays on Cylinder 4 (P0304), you know the injector is innocent and must check mechanical cylinder compression.