Cummins/Onan DGFB troubleshooting: 87 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan DGFB — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Remedy |
|---|---|---|
| F01 | Generator does not start. | Check the battery voltage and ensure it is above 12V. Verify that the fuel supply is adequate and check for any fuel system issues. Refer to the Fault Code Table for further troubleshooting. |
| F02 | Generator produces low output power. | Check the air filter for blockage or damage. Verify that the fuel supply is adequate and check for any fuel system issues. Refer to the Fault Code Table for further troubleshooting. |
| F03 | Generator produces excessive noise. | Check the engine oil level and ensure it is within the recommended range. Verify that all components are properly tightened, including bolts and nuts. Refer to the Fault Code Table for further troubleshooting. |
| F04 | Generator produces excessive vibration. | Check the engine mounts for any damage or wear. Verify that all components are properly tightened, including bolts and nuts. Refer to the Fault Code Table for further troubleshooting. |
| F05 | Generator produces excessive exhaust smoke. | Check the air filter for blockage or damage. Verify that the fuel supply is adequate and check for any fuel system issues. Refer to the Fault Code Table for further troubleshooting. |
| F06 | Generator produces excessive heat. | Check the cooling system for any leaks or blockages. Verify that the coolant level is within the recommended range. Refer to the Fault Code Table for further troubleshooting. |
| F07 | Generator produces excessive oil consumption. | Check the engine oil level and ensure it is within the recommended range. Verify that all components are properly tightened, including bolts and nuts. Refer to the Fault Code Table for further troubleshooting. |
| F08 | Generator produces excessive fuel consumption. | Check the air filter for blockage or damage. Verify that the fuel supply is adequate and check for any fuel system issues. Refer to the Fault Code Table for further troubleshooting. |
| 121 | Speed Signal Lost | |
| 135 | Oil Pressure Sensor High | |
| 141 | Oil Pressure Sensor Low | |
| 143 | Pre-Low Oil Pressure Sensor | |
| 144 | Coolant Temperature Sensor High | |
| 145 | Coolant Temperature Sensor Low | |
| 146 | Pre-High Cool Temp | |
| 151 | High Coolant Temp | |
| 197 | Low Coolant Level | |
| 234 | Overspeed | |
| 235 | Low Coolant Level | |
| 359 | Fail to Start | |
| 415 | Low Oil Pressure | |
| 441 | Low Battery Voltage | |
| 442 | High Battery Voltage | |
| 1123 | Shutdown After Battle Short | |
| 1124 | Delayed Shutdown | |
| 1131 | Battle Short Active | |
| 1244 | Engine Normal Shutdown | |
| 1311 | Customer Inputs #1 | |
| 1312 | Customer Inputs #2 | |
| 1317 | Customer Inputs #3 | |
| 1318 | Customer Inputs #4 | |
| 1334 | Crit Scaler OR | |
| 1335 | Non-Crit Scaler OR | |
| 1416 | Fail to Shutdown | |
| 1417 | Power Down Failure | |
| 1433 | Emergency Stop | |
| 1434 | Remote Emergency Stop | |
| 1435 | Low Coolant Temperature | |
| 1438 | Fail to Crank | |
| 1442 | Weak Battery | |
| 1443 | Battery Failed | |
| 1444 | KW Overload | |
| 1445 | Short Circuit | |
| 1446 | High AC Voltage | |
| 1447 | Low AC Voltage | |
| 1448 | Under Frequency | |
| 1449 | Over Frequency | |
| 1461 | Loss of Field | |
| 1466 | Modem Failure | |
| 1468 | Network Error | |
| 1469 | Speed/Hz Match | |
| 1471 | Over Current | |
| 1472 | Over Current | |
| 2335 | Excitation Fault | |
| 2336 | Memory Error | |
| 2341 | High Control Temperature | |
| 2342 | Too Long in Idle | |
| 2967 | Governor Fault | |
| 2968 | AVR Fault | |
| 2969 | LON Failure | |
| 2972 | Field Overload |
| Symptom | Cause | Remedy |
|---|---|---|
| Generator does not start | Check the fault codes and refer to the troubleshooting table for specific issues. Ensure that all connections are secure, and the control panel is powered on. | |
| Generator produces low voltage output | Refer to the fault codes and troubleshooting table for possible causes such as a faulty alternator or incorrect settings. Check the generator's load and ensure it is within the rated capacity. | |
| Generator produces high voltage output | Refer to the fault codes and troubleshooting table for possible causes such as a faulty alternator or incorrect settings. Check the generator's load and ensure it is within the rated capacity. | |
| Generator produces inconsistent voltage output | Refer to the fault codes and troubleshooting table for possible causes such as a faulty alternator or incorrect settings. Check the generator's load and ensure it is within the rated capacity. | |
| Generator produces inconsistent frequency output | Refer to the fault codes and troubleshooting table for possible causes such as a faulty alternator or incorrect settings. Check the generator's load and ensure it is within the rated capacity. | |
| Generator produces noise during operation | Refer to the fault codes and troubleshooting table for possible causes such as a faulty alternator or incorrect settings. Check the generator's load and ensure it is within the rated capacity. | |
| Generator produces excessive heat | Refer to the fault codes and troubleshooting table for possible causes such as a faulty alternator or incorrect settings. Check the generator's load and ensure it is within the rated capacity. | |
| Generator produces smoke | Refer to the fault codes and troubleshooting table for possible causes such as a faulty alternator or incorrect settings. Check the generator's load and ensure it is within the rated capacity. | |
| The engine does not start | The starter will disengage after a specified period of time and the control will indicate an overcrank shutdown. | Place the O/Manual/Auto switch in the O position and press the Fault Acknowledge/Reset button. Before attempting to restart, wait two minutes for the starter motor to cool and then repeat the starting procedure. If the engine does not run after a second attempt, refer to the Troubleshooting section. |
| LO OIL PRES lamp lights. Engine shuts down. | Check oil level, lines and filters. If oil system is OK but oil level is low, replenish. Reset control and restart. Contact an authorized service center if oil pressure is not in the range of 25 to 40 psi (172 to 275 kPa). | |
| 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. Reset the control and restart after correcting the problem. Contact an authorized service center for service if none of the above. | |
| Engine runs and then shuts down, OVERSPEED lamp lights. | Indicates engine has exceeded normal operating speed. Contact an authorized service center 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 diesel fuel supply is running low. Check fuel supply and replenish as required. | |
| 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. | |
| LO ENG TEMP lamp lights. Set is in standby mode but is not operating. | A. Coolant heater not connected to power supply. Check for blown fuse or disconnected heater cord and correct as required. b. Check for low coolant level and replenish if required. Look for possible coolant leakage points and repair as required. c. Contact an authorized service center for service 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. | |
| 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. Contact an authorized service center for service. | |
| Engine starts from generator control panel but will not start automatically or from a remote panel. | Remote circuit breaker is tripped. Reset breaker and restart. Contact an authorized service center if breaker trips after resetting. | |
| 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. Emergency stop button (if equipped) pushed in. To reset, pull switch out and move Run/Stop/Remote switch to Stop position. Then push test switch to Reset/Lamp position. e. Contact an authorized service center if none of the above. | |
| No AC output voltage. | Field breaker is tripped. Reset breaker. Contact an authorized service center if voltage buildup causes breaker to trip. | |
| Green RUN lamp does not light following engine startup. | Indicates possible Start/Disconnect relay failure. Contact an authorized service center for assistance. | |
| PRE HI ENGINE TEMP lamp lights. Engine continues to operate. | Indicates engine has begun to overheat and engine temperature has risen to approximately 215°F (102°C). | If generator is powering non-critical and critical loads and cannot be shut down, use the following: a. Reduce load if possible by turning off non-critical loads. b. Check air inlets and outlets and remove any obstructions to airflow. |
| PRE LO OIL PRES lamp lights. Engine continues to operate. | Indicates engine has overheated (engine temperature has risen above 222°F/106°C) or coolant level is low (sets with coolant level sensor). | |
| Status Indicators are not functioning properly. | Check the status indicators for any visible damage or loose connections. If the issue persists, refer to the Fault Code Table for further troubleshooting. | |
| Line Circuit Breaker (Optional) trips frequently. | Check the circuit breaker for any visible damage or loose connections. Verify that the generator's load is within the rated capacity of the circuit breaker. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: The starter will disengage after a specified period of time and the control will indicate an overcrank shutdown.. See the table for the matching fixes.
Documented causes: Indicates engine has begun to overheat and engine temperature has risen to approximately 215°F (102°C).. See the table for the matching fixes.
Documented causes: Indicates engine has overheated (engine temperature has risen above 222°F/106°C) or coolant level is low (sets with coolant level sensor).. See the table for the matching fixes.