Cummins/Onan 45.0 DEF-15R troubleshooting: 4 fault codes and 23 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan 45.0 DEF-15R — 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 | Cause | 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, then back to the required running position | |
| Fault lamp lights immediately after engine starts | Overspeed condition as engine starts | Check for overspeed condition as engine starts |
| Fault lamp lights and engine shuts down after running for a period | Oil level (engine will shut down if sensor is closed) | Check oil level |
| Fault lamp lights and engine shuts down after running for a period | Oil system fault | Check engine manual for troubleshooting oil system |
| Fault lamp lights and engine shuts down after running for a period | 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 |
| Fault lamp lights and engine shuts down after running for a period | Faulty oil pressure sensor or faulty high engine temperature sensor | 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 | Fuel supply problem | Check fuel supply |
| Fault lamp lights, no fault exists | Faulty engine monitor board | 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 | Fuel supply problem | Check fuel supply |
| Low oil pressure shutdown | Oil level | Check oil level; replenish if necessary |
| Low oil pressure shutdown | Faulty sensor (faulty sensor will shut down engine) | Check sensor |
| Low oil pressure shutdown | Oil system fault | Refer to engine service manual for troubleshooting guide for oil system |
| High engine temperature shutdown | Coolant level | Check coolant level; replenish if necessary |
| High engine temperature shutdown | City water cooled sets — water flow, valves, etc. | Check water flow, valves, etc. |
| High engine temperature shutdown | Sensor or thermostat | Check sensor; check thermostat |
| High engine temperature shutdown | Radiator model — fan belts, radiator obstructions, etc. | Check fan belts, radiator for obstructions, etc. |
| Overspeed shutdown | Governor and throttle linkages; overspeed switch | Check governor and throttle linkages for freedom of movement; check overspeed switch |
| Overspeed light on, no shutdown | Faulty engine monitor board | Disconnect wire at TB11-29; light on after reset: replace engine monitor board |
| Low oil pressure light ON. No shutdown | Faulty engine monitor board | Disconnect wire at TB11-30; light ON after relay reset: replace engine monitor board |
| High engine temperature light ON. No shutdown | Faulty engine monitor board | Disconnect wire at TB11-31; light ON after relay reset: replace engine monitor board |
| "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.
Documented causes: Oil level (engine will shut down if sensor is closed); Oil system fault; High engine temperature; Faulty oil pressure sensor or faulty high engine temperature sensor. See the table for the matching fixes.
Documented causes: Coolant level; City water cooled sets — water flow, valves, etc.; Sensor or thermostat; Radiator model — fan belts, radiator obstructions, etc.. See the table for the matching fixes.
Documented causes: Oil level; Faulty sensor (faulty sensor will shut down engine); Oil system fault. See the table for the matching fixes.