P0300: Random/Multiple Cylinder Misfire Detected

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.

• Combustion misfiring detected.

• 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

• 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

1. 1Scan and record all codes; note cylinder-specific codes (P0301–P0306) and fuel/rail codes (P0087, P0191).
2. 2Read live misfire counters per cylinder to see if one or several cylinders dominate.
3. 3Check freeze-frame for RPM, load, fuel temperature, and rail pressure when the misfire set.
4. 4Perform an injector return (back-leakage) test to find a leaking injector.
5. 5Verify rail pressure tracks commanded values; rule out a fuel delivery shortfall.
6. 6Test glow plugs and the glow control module for cold-start misfires.
7. 7If fuel and glow systems are good, perform a compression/leak-down test to assess mechanical health.

1. 1Replace a worn, clogged, or leaking injector on the affected cylinder.
2. 2Restore fuel rail pressure by fixing the supply or pump fault.
3. 3Replace a failed glow plug causing cold-start misfire.
4. 4Purge air ingress from the fuel system and reseal connections.
5. 5Address low/uneven compression with mechanical repair if confirmed.

• Fuel injector(s)~$250–$500 each
• Glow plugs / glow plug module~$120–$400