Cummins/Onan 45 kWEM troubleshooting: 8 fault codes and 21 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan 45 kWEM — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Cause | Remedy |
|---|---|---|---|
| LO ENG TEMP | Indicates engine coolant heater is not operating standby mode but is not operating. | A. Coolant heater not connected to power supply. b. Check for low coolant level and replenish if required. Look for possible coolant leakage points and repair as required. c. Contact an Onan dealer or distributor if none of the above. | |
| FAULT 1 or FAULT 2 | The standard undesignated fault functions are lights; Engine shuts down immediately, programed to shut down the set when a fault is sensed. Fault 1 is time-delayed while Fault 2 is immediate. | ||
| FAULT LAMP | *13. Fault lamp lights but no fault exists. Engine gauges show oil pressure, engine temperature and frequency (speed) are within normal limits. | Reset control. If control will not reset, the monitor board or a sensor may be at fault. Contact an Onan dealer or distributor for service. | |
| REMOTE CIRCUIT BREAKER | *14. Remote circuit breaker is tripped. Reset breaker but will not start automatically or from a remote panel (Note: Run/Stop/Remote switch must be in the REMOTE position for automatic or remote starting). | ||
| ENGINE WILL NOT CRANK | *15. Engine will not crank. | A. Fault lamp on. Correct fault and reset control. b. Poor battery cable connections ... Clean the battery cable terminals and tighten all connections. c. Discharged or defective battery; Recharge or replace the battery. d. Contact an Onan dealer or distributor for assistance if none of the above. | |
| NO AC OUTPUT VOLTAGE | *16. No AC output voltage. | Field breaker is tripped. Reset breaker. Contact an Onan dealer or distributor if voltage buildup causes breaker to trip. | |
| GREEN RUN LAMP | *17. Green RUN lamp does not light following engine start-up. | Indicates possible Start/Disconnect relay failure. Contact an Onan dealer or distributor for assistance. | |
| OVERCRANK | *6. OVERCRANK lamp lights and engine stops cranking. | A. Check for empty fuel tank, fuel leaks, or plugged fuel lines and correct as required. b. Check for dirty fuel filter and replace if necessary (see Maintenance section), c. Check for dirty or plugged air filter and replace if necessary (see Maintenance section). d. Check for loose connections in the ignition primary, ignition secondary, or solenoid valve |
| Symptom | Cause | Remedy |
|---|---|---|
| LO ENG TEMP lamp lights. Set is in standby mode but is not operating. (Lamp lights when engine water jacket temperature is 70°F (21°C) or lower. Since the lamp goes out after the engine warms up, there should be no cause for alarm even during initial generator set operation). | Indicates engine coolant heater is not operating or is not circulating coolant; Coolant heater not connected to power supply; Low coolant level; Possible coolant leakage points | Check for blown fuse or disconnected heater cord and correct as required; Check for low coolant level and replenish if required. Look for possible coolant leakage points and repair as required; Contact an Onan dealer or distributor if none of the above |
| The FAULT 1 or FAULT 2 fault lamp lights; Engine shuts down immediately, engine runs for several seconds and then shuts down, or engine continues to run. | The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time-delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay modes. | |
| Fault lamp lights but no fault exists. Engine gauges show oil pressure, engine temperature and frequency (speed) are within normal limits. | The monitor board or a sensor may be at fault | Reset control. If control will not reset, the monitor board or a sensor may be at fault. Contact an Onan dealer or distributor for service |
| Engine starts from generator control panel but will not start automatically or from a remote panel (Note: Run/Stop/Remote switch must be in the REMOTE position for automatic or remote starting). | Remote circuit breaker is tripped | Reset breaker and restart. Contact an Onan dealer or distributor if breaker trips after resetting |
| Engine will not crank. | Fault lamp on | Correct fault and reset control |
| Engine will not crank. | Poor battery cable connections | Clean the battery cable terminals and tighten all connections |
| Engine will not crank. | Discharged or defective battery | Recharge or replace the battery |
| Engine will not crank. | Possible fault with control or starting system | Contact an Onan dealer or distributor for assistance if none of the above |
| No AC output voltage. | Field breaker is tripped | Reset breaker. Contact an Onan dealer or distributor if voltage buildup causes breaker to trip |
| Green RUN lamp does not light following engine start-up. | Possible Start/Disconnect relay failure | Contact an Onan dealer or distributor for assistance |
| OVERCRANK lamp lights and engine stops cranking. | Possible fuel or ignition system problem; Empty fuel tank, fuel leaks, or plugged fuel lines; Dirty fuel filter; Dirty or plugged air filter; Loose connections in the ignition primary, ignition secondary, or solenoid valve circuits | Check for empty fuel tank, fuel leaks, or plugged fuel lines and correct as required; Check for dirty fuel filter and replace if necessary (see Maintenance section); Check for dirty or plugged air filter and replace if necessary (see Maintenance section); Check for loose connections in the ignition primary, ignition secondary, or solenoid valve circuits and correct as required; Reset the control and restart after correcting the problem. Contact an Onan dealer or distributor for service if none of the above; Check choke adjustment for dual-fuel system |
| Engine runs, shuts down, and LO OIL PRES lamp lights. | Possible fuel or ignition system problem; Empty fuel tank, fuel leaks, or plugged fuel lines; Dirty fuel filter; Dirty or plugged air filter; Loose connections in the ignition primary, ignition secondary, or solenoid valve circuits | Check for empty fuel tank, fuel leaks, or plugged fuel lines and correct as required; Check for dirty fuel filter and replace if necessary (see Maintenance section); Check for dirty or plugged air filter and replace if necessary (see Maintenance section); Check for loose connections in the ignition primary, ignition secondary, or solenoid valve circuits and correct as required; Reset the control and restart after correcting the problem. Contact an Onan dealer or distributor for service if none of the above; Check choke adjustment for dual-fuel system |
| Engine runs and then shuts down, OVERSPEED lamp lights. | Indicates engine has exceeded normal operating speed | Contact an Onan dealer or distributor for service |
| SWITCH OFF lamp flashes. | Indicates Run/Stop/Remote switch is in the STOP position which will prevent automatic starting if an automatic transfer switch is used | Move the Run/Stop/Remote switch to the REMOTE position for automatic starting |
| LO FUEL lamp lights. Engine continues to run. | Indicates gasoline fuel supply is running low | Check fuel supply and replenish if necessary. If set has a combination Gas/Gasoline fuel system, place fuel selector switch in the GAS position to change over to natural gas operation |
| LO FUEL lamp lights. Engine shuts down and LO OIL PRES lamp lights. | Indicates engine has run out of fuel | Check fuel level and replenish as required |
| Green RUN lamp lights following engine start-up. | Indicates all engine systems are normal | No corrective action required |
| PRE HI ENGINE TEMP lamp lights. Engine continues to operate. | Indicates engine has begun to overheat and engine temperature has risen to approximately 205°F (97°C) | If engine can be stopped, follow the procedures in step 3. Use the following procedures if generator is powering critical loads and cannot be shut down: Check air inlets and outlets and remove any obstructions to airflow; Open doors or windows in generator area to increase ventilation; Reduce load if possible by turning off non-critical loads |
| HIGH ENG TEMP lamp lights. Engine shuts down. | Indicates engine has overheated and engine temperature has risen above 215°F (102°C) or coolant level is low (sets with coolant level sensor) | Allow engine to cool down completely before proceeding with the following checks: Check coolant level and replenish if low. Look for possible coolant leakage points and repair if necessary; Check for obstructions to cooling airflow and correct as necessary; Check for a slipping fan belt and tighten if loose; Reset control and restart after locating and correcting problem. Contact an Onan dealer or distributor if none of the above |
| PRE LO OIL PRES lamp lights. Engine continues to operate. | Indicates engine oil pressure has dropped to 20 psi (138 kPa) | If engine can be stopped, follow procedures in step 5. If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow step 5 procedure |
| LO OIL PRES lamp lights. Engine shuts down. | Indicates engine oil pressure has dropped to 14 psi (97 kPa) | Check oil level and replenish if low. Reset control and restart. Contact an Onan dealer or distributor if oil pressure is not in the range of 35 to 60 psi (241 to 414 kPa) |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Fault lamp on; Poor battery cable connections; Discharged or defective battery; Possible fault with control or starting system. See the table for the matching fixes.
Documented causes: Indicates engine coolant heater is not operating or is not circulating coolant; Coolant heater not connected to power supply; Low coolant level; Possible coolant leakage points. See the table for the matching fixes.
Documented causes: The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time-delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay modes.. See the table for the matching fixes.