Cummins/Onan B48 troubleshooting: 9 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan B48 — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Remedy |
|---|---|
| Dizziness | Get out into fresh air immediately, shut down the unit and do not use until it has been inspected. |
| Muscular Twitching | Get out into fresh air immediately, shut down the unit and do not use until it has been inspected. |
| Vomiting | Get out into fresh air immediately, shut down the unit and do not use until it has been inspected. |
| Weakness and Sleepiness | Get out into fresh air immediately, shut down the unit and do not use until it has been inspected. |
| Inability to Think Coherently | Get out into fresh air immediately, shut down the unit and do not operate until it has been inspected and repaired. |
| Excess oil can cause high oil consumption, high operating temperatures, and oil foaming. | Do not overfill crankcase. Run engine until thoroughly warm before draining oil. |
| The reed valve must be flat with no sign of a crease. | Assemble using a new gasket. Torque capscrew to 1-2 ft-lbs (1 -3 Nm). |
| Oil pump is worn and needs replacement. | Install a new pump assembly if any parts are worn. |
| By-pass valve is not operating normally. | Inspect plunger action by removing the 3/8 x 24 x 7/8 cap screw, and then remove spring and plunger with a magnet tool. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.