Cummins/Onan Marquis troubleshooting: 9 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan Marquis — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Remedy |
|---|---|
| Dizziness | IF YOU OR ANYONE ELSE EXPERIENCE ANY OF THESE SYMPTOMS, GET OUT INTO THE FRESH AIR IMMEDIATELY. If symptoms persist, seek medical attention. Shut down the unit and do not operate until it has been inspected and repaired. |
| Muscular Twitching | IF YOU OR ANYONE ELSE EXPERIENCE ANY OF THESE SYMPTOMS, GET OUT INTO THE FRESH AIR IMMEDIATELY. If symptoms persist, seek medical attention. Shut down the unit and do not operate until it has been inspected and repaired. |
| Vomiting | IF YOU OR ANYONE ELSE EXPERIENCE ANY OF THESE SYMPTOMS, GET OUT INTO THE FRESH AIR IMMEDIATELY. If symptoms persist, seek medical attention. Shut down the unit and do not operate until it has been inspected and repaired. |
| Weakness and Sleepiness | IF YOU OR ANYONE ELSE EXPERIENCE ANY OF THESE SYMPTOMS, GET OUT INTO THE FRESH AIR IMMEDIATELY. If symptoms persist, seek medical attention. Shut down the unit and do not operate until it has been inspected and repaired. |
| Inability to Think Coherently | IF YOU OR ANYONE ELSE EXPERIENCE ANY OF THESE SYMPTOMS, GET OUT INTO THE FRESH AIR IMMEDIATELY. If symptoms persist, seek medical attention. Shut down the unit and do not operate until it has been inspected and repaired. |
| If the genset fails to start | See the Troubleshooting Guide in the Operator’s Manual |
| Fuel leaks are found | Stop the set immediately, close off the fuel supply and have the leak(s) repaired |
| Exhaust system for leaks is examined | Stop the set and have the exhaust system repaired immediately |
| Generator set is excessively noisy | Have it inspected and repaired immediately by an authorized Onan service center |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.