Diagnóstico / Códigos de avería
Random/Multiple Cylinder Misfire Detected
The ECU detected misfires across multiple or random cylinders — on the OM642 diesel this usually points to injectors, fuel delivery, or compression rather than spark.
Qué significa este código
P0300 on the Mercedes Sprinter VS30 indicates random or multiple-cylinder combustion misfires. On a diesel like the OM642 there are no spark plugs, so misfires trace to fuel delivery and combustion: worn or leaking injectors, low rail pressure, glow plug faults (cold-start misfire), air in the fuel, low compression, or EGR/intake problems. If the misfire is isolated to one cylinder you'll usually also see a cylinder-specific code (P0301–P0306). P0300 means the ECU couldn't attribute the misfire to a single cylinder, or several are affected. Diagnose by reading the misfire counters per cylinder, checking injector condition and return flow, verifying rail pressure, and confirming glow plug operation for cold-start cases.
Descripción oficial
- Combustion misfiring detected.
Síntomas
- Rough idle or shaking, especially when cold
- Hesitation, stumbling, or power loss
- Check engine light (may flash under heavy misfire)
- Hard starting, particularly in cold weather
- Increased smoke or fuel smell
- Uneven engine note
Advertencia — revísalo pronto
The ECU detected misfires across multiple or random cylinders — on the OM642 diesel this usually points to injectors, fuel delivery, or compression rather than spark.
Causas posibles
- Worn, clogged, or leaking fuel injectors (common on OM642)
- Low fuel rail pressure / fuel delivery fault
- Faulty glow plugs or glow plug module (cold-start misfire)
- Air ingress in the fuel system
- Low or uneven cylinder compression
- EGR/intake faults disturbing combustion
Pasos de diagnóstico
- Scan and record all codes; note cylinder-specific codes (P0301–P0306) and fuel/rail codes (P0087, P0191).
- Read live misfire counters per cylinder to see if one or several cylinders dominate.
- Check freeze-frame for RPM, load, fuel temperature, and rail pressure when the misfire set.
- Perform an injector return (back-leakage) test to find a leaking injector.
- Verify rail pressure tracks commanded values; rule out a fuel delivery shortfall.
- Test glow plugs and the glow control module for cold-start misfires.
- If fuel and glow systems are good, perform a compression/leak-down test to assess mechanical health.
Reparaciones recomendadas
- Replace a worn, clogged, or leaking injector on the affected cylinder.
- Restore fuel rail pressure by fixing the supply or pump fault.
- Replace a failed glow plug causing cold-start misfire.
- Purge air ingress from the fuel system and reseal connections.
- Address low/uneven compression with mechanical repair if confirmed.
Piezas que podrías necesitar
- Fuel injector(s)~$250–$500 each
- Glow plugs / glow plug module~$120–$400
Preguntas frecuentes
Diesels don't have spark plugs — so what causes a P0300 misfire?
On the OM642 it's about fuel and compression, not spark. Leaking or worn injectors, low rail pressure, air in the fuel, weak glow plugs (cold starts), or low compression are the usual culprits.
Is a flashing check engine light with P0300 serious?
Yes. A flashing light means an active, heavy misfire that can damage the after-treatment system. Reduce load and get it diagnosed promptly rather than continuing to drive hard.