Cummins/Onan 45.0 DEF-9XR troubleshooting: 13 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan 45.0 DEF-9XR — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Remedy |
|---|---|---|
| Low oil pressure shutdown | Low oil pressure shutdown. | Check— a. Oil level. Replenish if necessary. b. Sensor. Faulty sensor will shut down engine. c. Refer to engine service manual for troubleshooting guide for oil system. |
| High engine temperature shutdown | *High engine temperature shutdown. | Check— a. Coolant level. Replenish if necessary. b. City water cooled sets. Check water flow, valves, etc. c. Check sensor; check thermostat. d. Radiator model, check fan belts, radiator for obstructions, etc. |
| Overspeed shutdown | Overspeed shutdown. | Check governor and throttle linkages for freedom of movement. Check overspeed switch. |
| Overspeed light on, no shutdown | Overspeed light on, no shutdown. | Disconnect wire at TB11-29. Light on after reset; replace engine monitor board. |
| Symptom | Remedy |
|---|---|
| Engine stops cranking and fault lamp lights, after cranking approximately 75 seconds. | See engine service manual for troubleshooting fuel system. After correcting problem, reset engine monitor relay by placing Run-Stop/Reset-Remote switch to Stop/Reset position, then back to the required running position. |
| Fault lamp lights immediately after engine starts. | Check for: Overspeed condition as engine starts. |
| Fault lamp lights and engine shuts down after running for a period. | Check the following: a. Oil level. Engine will shut down if sensor is closed. b. Check engine manual for troubleshooting oil system. c. High engine temperature. Check coolant level; check water flow (city water cooled systems); check radiator for free air flow, and fan belts for tightness. See engine manual for troubleshooting cooling system. d. Check for faulty oil pressure sensor or faulty high engine temperature sensor. |
| Engine runs, shuts down and cranks for 75-seconds. Cranking cycle stops; fault lamp lights. | Check fuel supply. |
| Fault lamp lights, no fault exists. | To check a no-fault condition, disconnect leads from TB11 terminals 29, 30 and 31. If fault lamp lights with leads disconnected, replace engine monitor board. Reconnect leads. |
| Overcrank fault lamp lights and engine stops cranking after approximately 75-seconds. | See engine service manual for troubleshooting fuel system. After correcting fault, reset engine monitor relay by placing Run-Stop/Reset-Remote switch to Stop/Reset position, depressing Reset button, then to the required running position. |
| Engine runs, shuts down, cranks for 75-seconds, cranking cycle stops, overcrank light ON. | Check fuel supply. |
| "Low oil pressure light ON. No shutdown." | Disconnect wire at TB11-30. Light ON after relay reset. Replace engine monitor board. |
| *"High engine temperature light ON. No shutdown." *NOTE: Not applicable on Pennsylvania State models. | Disconnect wire at TB11-31. Light ON after relay reset. Replace engine monitor board. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.