Cummins/Onan 50.0DDB-15R troubleshooting: 22 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan 50.0DDB-15R — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Cause | Remedy |
|---|---|---|
| Fault lamp lights and engine stops cranking after approximately 75 seconds | See engine service manual for troubleshooting fuel system, ignition system, etc.; After correcting problem, reset the engine monitor by moving run-stop/reset-remote switch to reset position; Release and return to run position | |
| Fault lamp lights immediately after engine starts | Overspeed condition as engine starts | |
| Fault lamp lights immediately after engine starts | High temperature condition | |
| Fault lamp lights immediately after engine starts | Faulty high engine temperature sensor or overspeed switch | |
| Fault lamp lights immediately after engine starts | Faulty starter disconnect | |
| Fault lamp lights after engine is running | Oil level — engine will shut down after approximately 12-1/2 seconds if low oil pressure sensor does not open | |
| Fault lamp lights after engine is running | Oil pressure sensor may be defective | |
| Fault lamp lights after engine is running | High engine temperature — caused by low coolant level, faulty thermostat, etc. | |
| Fault lamp lights after engine is running | Faulty high engine temperature sensor | |
| Fault lamp lights after engine is running | Faulty starter disconnect | |
| Fault lamp lights — no fault condition exists | Be certain that no fault condition exists; Disconnect lead 29, 30 and 31 from TB11 inside control box (refer to wiring diagram); If fault lamp still lights with leads disconnected, remove and replace engine monitor plug-in printed circuit board | |
| Overcrank fault lamp lights and engine stops cranking after approximately 75 seconds | See engine service manual for troubleshooting fuel system, ignition system, etc.; After correcting fault, reset monitor by moving run-stop/reset-remote switch to reset position, then to either run or remote to restart engine | |
| Overcrank fault lamp lights after engine has run for approximately 75 seconds | Replace start-disconnect circuit board | |
| High engine temperature lamp lights as soon as engine starts | Defective sensor or actual high temperature condition | Check for defective sensor or actual high temperature condition |
| Low oil pressure lamp lights after engine is running | Oil level — engine will shut down after approximately 12-1/2 seconds if oil pressure is low | |
| High engine temperature lamp lights after engine is running | Defective thermostat/thermostats | |
| High engine temperature lamp lights after engine is running | Low coolant level | |
| High engine temperature lamp lights after engine is running | Defective high engine temperature sensor | |
| Overspeed lamp lights — no fault condition exists | Replace overspeed circuit board | |
| Low oil pressure fault lamp lights — no fault condition exists | Be certain that no fault condition exists; Disconnect lead 30 from TB11 inside control box (refer to wiring diagram); If low oil pressure lamp still lights, remove and replace engine monitor plug-in printed circuit board | |
| High engine temperature fault lamp lights — no fault condition exists | Be certain that no fault condition exists; Remove lead 31 from TB11 inside control box (refer to wiring diagram); If high engine temperature lamp still lights, remove and replace engine monitor plug-in printed circuit board | |
| When pressing test lamp button — one or more fault lamps do not light (engine not running) | Fault lamp/lamps burned out | Replace |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Oil level — engine will shut down after approximately 12-1/2 seconds if low oil pressure sensor does not open; Oil pressure sensor may be defective; High engine temperature — caused by low coolant level, faulty thermostat, etc.; Faulty high engine temperature sensor. See the table for the matching fixes.
Documented causes: Overspeed condition as engine starts; High temperature condition; Faulty high engine temperature sensor or overspeed switch; Faulty starter disconnect. See the table for the matching fixes.
Documented causes: Defective thermostat/thermostats; Low coolant level; Defective high engine temperature sensor. See the table for the matching fixes.