Cummins/Onan DGGD troubleshooting: 19 fault codes and 84 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan DGGD — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Cause | Remedy |
|---|---|---|---|
| FAULT 1 | 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 2 | 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. | |
| 14 | Remote circuit breaker is tripped. | Reset breaker and restart. Contact an authorized service center if breaker trips after resetting. | |
| 16 | Engine will not crank. | Indicates possible fault with control or starting system. Check for the following conditions: 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. | |
| 17 | No AC output voltage. | Field breaker is tripped. Reset breaker. Contact an authorized service center if voltage buildup causes breaker to trip. | |
| 18 | RUN or fault lamp(s) does not light when Lamp Test switch is engaged. | Contact an authorized service center for assistance. | |
| 19 | Green RUN lamp does not light following engine startup. | Indicates possible Start/Disconnect relay failure. Contact an authorized service center for assistance. | |
| F1 | The engine does not crank in Run mode — Fuse F1 (see Figure 3-4) on ECM has blown (no voltage [B+] at ECM TB1-8). | The wire between ECM TB1-8 and starter terminal B1-SW or the wires between TB1-8 – resistor/diode assembly – battery charging alternator may be loose and shorting to ground. | Repair as necessary and replace the fuse with one of the same type and amp rating (20 A). If fuse continues to blow, service or replace the starter, relay K4, or the resistor/diode assembly. |
| S12 | The engine does not crank in Run mode — The Run-Stop-Remote switch (S12) or wiring is faulty. | The Run-Stop-Remote switch (S12) or wiring is faulty. | Disconnect pin connector J4 from the ECM and check for electrical continuity (zero ohms) between switch terminals 2 and 3 when the switch is in the Run position and between terminals 1 and 2 when it is in the Remote position. Replace the switch if either set of contacts is faulty; If the switch works, check for electrical continuity (zero ohms) between J4-6 and J4-7 on the wire harness when the switch is in the Run position and between J4-5 and J4-7 when the switch is in the Remote position. Repair the wire harness if there is no electrical continuity in either position of the switch. |
| A15 | The engine does not crank in Run mode — The Time Delay Start/Stop Module (A15) is malfunctioning. | The Time Delay Start/Stop Module (A15) is malfunctioning. | Check for constant B+ at A15 terminal TB1-4. Check for run signal at ECM TB1-5. Voltage at A15 TB1-6 should be at B+ at the end of the start delay period. Check wiring and connections from A15 TB1-6 to ECM TB1-6. |
| F3 | The engine does not crank in Remote mode — There is no remote circuit signal (12 VDC at auxiliary relay board A28-TB1-6) because fuse F3 on the ECM has blown. | Fuse F3 on the ECM has blown. | Replace the fuse with one of the same type and amp rating (15 A); If fuse F3 blows again, find and repair the fault in the remote control circuit, such as a loose wire that may be shorting to ground or a shorted relay coil or other component. See Section 8 for remote connections. |
| A28 | The engine does not crank in Remote mode — Auxiliary relay board A28 is not functioning properly. | Auxiliary relay board A28 is not functioning properly. | Check for misconnections (see Section 8) or loose connections and replace auxiliary relay board A28 if there is 12 VDC at terminal A28-TB1-6 but not at A28-J2-6. |
| F2 | The engine cranks but does not start — Fuse F2 on the ECM has blown. | Fuse F2 on the ECM has blown. | Replace fuse with one of the same type and amp rating. If fuse F2 blows again, the wire between ECM TB1-10 and engine block terminal T26, or a wire between terminal T26 and an accessory may be loose or shorting to ground. |
| K1 | The engine cranks but does not start — Fuel solenoid K1 does not energize. | Fuel solenoid K1 does not energize. | Fuel solenoid not energized by the ECM. Check for B+ at ECM TB1-10 when cranking. If no voltage present and fuse F2 is good replace ECM; Connect B+ to fuel solenoid (K1) terminal BAT. Replace the fuel solenoid if does not “click” when energized. If fuel solenoid is working, check for blocked fuel line or fuel filter. |
| CB21 | No output voltage — Field circuit breaker CB21 has TRIPPED. | Field circuit breaker CB21 has TRIPPED. | RESET the circuit breaker. If it keeps tripping, troubleshoot according to the chart, Field Circuit Breaker Keeps Tripping. |
| CB21 | No output voltage — Field circuit breaker CB21 is faulty. | Field circuit breaker CB21 is faulty. | Shut down the set, attempt to RESET the circuit breaker and disconnect either lead. Replace the circuit breaker if there is measurable resistance across the terminals. |
| VR21 | Output voltage is too high or too low — Voltage Regulator VR21 is faulty. | Voltage Regulator VR21 is faulty. | Replace the voltage regulator. |
| VR21 | Output voltage is unstable — Voltage Regulator VR21 is faulty. | Voltage Regulator VR21 is faulty. | Replace the voltage regulator. |
| VR21 | The field circuit breaker keeps tripping — Voltage Regulator VR21 is faulty. | Voltage Regulator VR21 is faulty. | Replace the voltage regulator. |
| Symptom | Cause | Remedy |
|---|---|---|
| Green RUN lamp lights following engine startup | Indicates all engine systems are normal. No corrective action required. | |
| PRE HI ENGINE TEMP lamp lights. Engine continues to operate. (Engine can be programmed to shut down.) | Engine has begun to overheat and engine temperature has risen to approximately 220°F (104°C) or coolant level is low on optionally wired sets | If generator is powering non-critical and critical loads and cannot be shut down: reduce load if possible by turning off non-critical loads; check air inlets and outlets and remove any obstructions to airflow. If engine can be stopped, follow procedure in step 3. |
| HI ENG TEMP lamp lights. Engine shuts down. | Engine has overheated (engine temperature has risen above 230°F/110°C) or coolant level is low | Allow engine to cool down completely before proceeding: 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 authorized service center if none of the above. |
| PRE LO OIL PRES lamp lights. Engine continues to operate. (Engine can be programmed to shut down.) | Engine oil pressure has dropped to 20 psi (138 kPa) | If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow step 5 procedure. If engine can be stopped, follow procedures in step 5. |
| LO OIL PRES lamp lights. Engine shuts down. NOTE: See also step 6. | Engine oil pressure has dropped to 14 psi (97 kPa) | 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. or Engine runs, shuts down, and LO OIL PRES lamp lights. | Possible fuel system problem | 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); reset the control and restart after correcting the problem; contact an authorized service center for service if none of the above. |
| OVERSPEED lamp lights and the engine shuts down. | Engine has exceeded normal operating speed | Contact an authorized service center for service. |
| SWITCH OFF lamp flashes. | 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. | 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. | 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. (Lamp lights when engine coolant 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.) | Engine coolant heater is not operating, not circulating coolant or ambient temperature too cold for heater to keep up with demand | Check for the following conditions: coolant heater not connected to power supply — 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 authorized service center if none of the above. |
| 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. |
| The BASIN (optional) fault lamp lights. Engine continues to run or is in standby mode. (Engine can be programmed to shut down.) | Fuel is leaking from inner tank to outer basin or the sensor may be defective | Contact an authorized service center for service. |
| Engine starts from generator control panel but will not start automatically or from a remote panel. (Note: The 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 authorized service center if breaker trips after resetting. |
| Engine will not crank. | Possible fault with control or starting system | Check for the following conditions: fault lamp on — correct fault and reset control; poor battery cable connections — clean the battery cable terminals and tighten all connections; discharged or defective battery — recharge or replace the battery; 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; 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. |
| RUN or fault lamp(s) does not light when Lamp Test switch is engaged. | Contact an authorized service center for assistance. | |
| Green RUN lamp does not light following engine startup. | Possible Start/Disconnect relay failure | Contact an authorized service center for assistance. |
| The engine does not crank in Run mode | The Emergency Stop switch has been used. (The switch button is lit.) | Pull the Emergency Switch button. To reset the engine control, push the Run-Stop-Remote switch to Stop and the Reset switch to Reset. Then push the Run-Stop-Remote switch to Run. |
| The engine does not crank in Run mode | A Fault Shutdown is being indicated by one of the red lights on the control panel. | Service the set as necessary. To reset the engine control, push the Run-Stop-Remote switch to Stop and the Reset switch to Reset. Then push the Run-Stop-Remote switch to Run. |
| The engine does not crank in Run mode | A LO Shutdown is being indicated on the day tank pump control panel. | Determine the cause and service as necessary (See Section 7). To reset the engine control, push the Run-Stop-Remote switch to Stop and the Reset switch to Reset. Then push the Run-Stop-Remote switch to Run or Remote. Note that the engine control will shut down unless the day tank control has been reset first. |
| The engine does not crank in Run mode | Cranking voltage is too low to crank the engine. | Clean and tighten or replace the positive (+) and negative (–) battery cable connectors and cables at the battery and the set; Recharge or replace the battery. Specific gravity for a fully charged battery is approximately 1.260 at 80° F (27° C); If the set is in standby service, install a battery charger; Replace the engine-driven battery charging alternator if normal battery charging voltage (12 to 14 VDC) is not obtained. |
| The engine does not crank in Run mode | The wire between ECM TB1-9 and starter terminal BAT is loose damaged or missing. | Check for battery voltage (12 VDC) between ECM TB1-9 (B+) and the grounding stud (–) on the floor of the control cabinet. Check, clean and tighten the connectors at both ends and replace the wire if it is damaged. |
| The engine does not crank in Run mode | The grounding strap between the control box and the battery negative (–) terminal or the ground wire between the control and engine ground is loose, damaged or missing. | Check for continuity (zero ohms) between the grounding stud on the bottom of the control box and the battery negative (–) terminal. If there is no continuity or the grounding strap is loose or damaged, repair as necessary. |
| The engine does not crank in Run mode | ECM is faulty. (Check fuses F1 and F4 and for B+ at TB1-9 again.) | Push the Run-Stop-Remote switch to Run and check for battery voltage (12 VDC) at ECM TB1-8. Replace ECM if there is no voltage at ECM TB1-8 but 12 VDC at ECM TB1-9. |
| The engine does not crank in Run mode | The wire between ECM TB1-8 and starter solenoid terminal SW is loose, damaged or missing. | Push the Run-Stop-Remote switch to Run and check for battery voltage (12 VDC) at starter solenoid terminal SW. If there is no voltage repair the wiring as necessary. |
| The engine does not crank in Run mode | The starter motor or solenoid is malfunctioning. | Push the Run-Stop-Remote switch to Run and check for battery voltage (B+) at starter solenoid terminal SW. Replace the starter motor if there is voltage but the motor does not function. |
| The engine does not crank in Remote mode | The Run-Stop-Remote switch is at Stop. (The Switch-Off light will be flashing, if provided.) | Push the Run-Stop-Remote switch to Remote. |
| The engine does not crank in Remote mode | The Emergency Stop switch has been used. (The switch button is lit.) | Pull the Emergency Switch button. To reset the engine control, push the Run-Stop-Remote switch to Stop and the Reset switch to Reset. Then push the Run-Stop-Remote switch to Remote. |
| The engine does not crank in Remote mode | A Fault Shutdown is being indicated by one of the red lights on the control panel. | Service the set as necessary. To reset the engine control, push the Run-Stop-Remote switch to Stop and the Reset switch to Reset. Then push the Run-Stop-Remote switch to Remote. |
| The engine does not crank in Remote mode | There is no remote circuit signal (12 VDC at auxiliary relay board A28-TB1-6) because the remote circuit is not functioning properly. | Apply 12 VDC to A28-TB1-6. If the engine cranks, find and repair the fault in the remote control circuit. See Section 8 for remote connections. |
| The engine does not crank in Remote mode | Same as Steps 3 through 11 in the RUN mode. | See steps 3 through 11 in the preceding RUN mode. |
| The engine cranks but does not start | The engine is not getting fuel. | Open any closed fuel shutoff valve; Fill the main fuel supply tank; Restore fuel pump prime according to the engine service manual. |
| The engine cranks but does not start | Low engine temperature is causing too low a cranking speed for starting. | Increase room temperature; Plug in, repair or install engine coolant heater; Replace the engine oil if it is not of the recommended viscosity for the ambient temperature. |
| The engine cranks but does not start | Cranking voltage is too low to reach required cranking speed. | While cranking the engine, measure voltage directly across the battery terminals and then immediately across the starter motor terminal and the grounding bolt on the block. Cable, terminal or relay contact resistance is too high if the difference is more than 2 volts. Service as necessary; Recharge or replace the battery. Specific gravity for a fully charged battery is approximately 1.260 at 80° F (27° C); Replace the engine-driven battery charging alternator if normal battery charging voltage is not between 12 and 14 volts. |
| The engine cranks but does not start | The air cleaner is blocked. | Service as necessary. |
| The engine cranks but does not start | Ignition system, fuel system or other engine malfunction. | Service according to the engine service manual. |
| The engine runs until fault shutdown | The OVERSPEED lamp comes on and the engine shuts down. | Reset the ECM by pushing the Run-Stop-Remote switch to Stop and the Reset switch to Reset and restart the set, monitoring engine speed. Readjust the cutout speed if it is lower than specified. Replace the overspeed module (PMG equipped sets) or the overspeed switch if it cannot be readjusted (see Section 3); Adjust the governor (see Section 6); If the governor cannot be adjusted to prevent shutdown due to overspeed, check for binding in the linkage. Repair and adjust the linkage as necessary. (A spring inside the actuator will resist movement, which is normal.); If the set still shuts down due to overspeed, re-install the magnetic speed pick-up unit to make sure the clearance with the flywheel gear teeth is correct. Replace the speed-pickup unit if output voltage at cranking speed is less than 2.5 VDC as measured at terminals 10 (–) and 11 (+) on the governor controller; Disconnect the actuator leads at governor controller terminals 4 and 5. Jumper the lead for terminal 4 to the BAT terminal on the starter solenoid and touch the lead for terminal 5 to a good ground on the block. Replace the actuator unit if it does not drive the linkage through its full travel when power is connected or return it when power is disconnected; Replace the governor controller if the set still shuts down due to overspeed. |
| The engine runs until fault shutdown | The LO OIL PRES lamp comes on and the engine shuts down. | Check the engine oil level, repair any oil leaks and fill to the proper level. Then reset the ECM by pushing the Run-Stop-Remote switch to Stop and the Reset switch to Reset; If the set still shuts down due to low oil pressure, restart the set and observe oil pressure while cranking the engine. Service the lubricating oil system according to the engine service manual if oil pressure is less than 14 psi (97 kPa). Replace the low oil pressure cutout switch if oil pressure is greater than 14 psi (97 kPa). See Section 3 to locate the switch. |
| The engine runs until fault shutdown | The HI ENG TEMP lamp comes on and the engine shuts down. | Check the engine coolant level, repair any coolant leaks and refill as necessary. Then reset the ECM by pushing the Run-Stop-Remote switch to Stop and the Reset switch to Reset; If the set still shuts down due to high engine temperature, start the engine and observe coolant temperature as the system heats up. If shutdown occurs before the coolant reaches 230° F (110° C), replace the high engine temperature cutout switch. If coolant temperature exceeds 230° F (110° C), clean and service the entire cooling system as required to restore full cooling capacity. See Section 3 to locate the switch. |
| The engine runs until fault shutdown | The FAULT 1 or FAULT 2 lamp comes on and the engine shuts down. | Service as required. (The customer has supplied the system fault indication switches. Either fault can be chosen to display the warning only. See Section 3.) If the shutdown was due to low frequency, the set probably ran out of fuel or the governor is out of adjustment. If the shutdown was due to over/under voltage, the voltage regulator may be out of adjustment. |
| The engine lacks power or is unstable | Fuel delivery to the genset is inadequate. | Check for clogged fuel lines and filters; Check for air in the fuel lines and repair all air leaks; Check fuel inlet and outlet restriction. Refer to Cummins B3.3 Series Engines Operation and Maintenance Manual Specifications section. |
| The engine lacks power or is unstable | The fuel is contaminated. | Connect the set to a supply of good quality fuel and run the set under various loads. Replace the contents of the fuel supply tank if there is a noticeable improvement in performance. |
| The engine lacks power or is unstable | The engine air filter element is dirty. | Replace the air filter element. |
| The engine lacks power or is unstable | The governor settings or linkage adjustment is incorrect. | Make governor settings and adjustments according to Section 6, Governor; If the governor cannot be adjusted for full power or stable speed, shut down the set and check for binding in the linkage. Repair and adjust the linkage as necessary. (A spring inside the actuator will resist opening the movement, which is normal.); Check the magnetic speed pick-up unit (MPU) clearance with flywheel. Replace the MPU if output voltage at cranking speed is less than 2.5 VDC measured at terminals 10 (–) and 11 (+) on the governor controller; Re-install the magnetic speed pick-up unit to make sure the clearance with the flywheel gear teeth is correct. Replace the speed-pickup unit if output voltage at cranking speed is less than 2.5 VDC as measured at terminals 10 (–) and 11 (+) on the governor controller; Disconnect the actuator leads at governor controller terminals 4 and 5. Jumper the lead for terminal 4 to the BAT terminal on the starter solenoid and touch the lead for terminal 5 to a good ground on the block. Replace the actuator unit if it does not drive the linkage through its full travel when power is connected or return it when power is disconnected; Replace the governor controller if it still cannot be adjusted for full power or stable speed. |
| The engine lacks power or is unstable | The engine fuel system (lift pump, injection pump, injectors, timing) is faulty. | Service the fuel system according to the engine service manual. |
| The engine lacks power or is unstable | The engine is worn. | Service the engine according to the engine service manual. |
| An amber warning lamp is on | The PRE LO OIL PRES lamp comes on while the engine is running. | Shut down the set if possible or disconnect non-critical loads. (Oil pressure will be less than 20 psi [138 kPa] but greater than 14 psi [97 kPa].) Service the engine lubricating system according to the engine service manual. |
| An amber warning lamp is on | The PRE HI ENG TEMP lamp comes on while the engine is running. | Shut down the set if possible or disconnect non-critical loads. (Engine temperature will be greater than 220° F [104° C] but less than 230° F [110° C].) Service the engine cooling system to restore full cooling capacity. |
| An amber warning lamp is on | The LOW ENGINE TEMPERATURE lamp comes on while the set is in standby. | Plug in, repair or install engine coolant heater. |
| An amber warning lamp is on | The LO FUEL lamp comes on. | Fill the main fuel supply tank with the appropriate grade of fuel. (The customer has supplied the fuel level switch to make use of this warning.) |
| An amber warning lamp is on | The Basin lamp comes on. | Indicates fuel is leaking from inner tank to outer basin or the sensor may be defective. Service as required. (The customer has supplied this sensor to make use of this warning.) |
| An amber warning lamp is on | The FAULT 1 or FAULT 2 lamp (may be a specifically labeled amber lamp) comes on. | Service as required. (The customer has supplied the system fault indicating switches. By means of selection jumpers, either fault may be chosen to shut down the engine. See Section 3, Engine Control.) |
| The green RUN lamp stays off but the set runs normally | The set mounted RUN lamp does not light, although the starter has disconnected normally and the engine is running. The remote RUN lamp does light (AC start disconnect is okay). | Press the panel Lamp Test switch and replace the run lamp bulb if it does not light; If the RUN lamp, wiring connections and battery charging alternator are all good and the RUN lamp does not light, replace the ECM. |
| The green RUN lamp stays off but the set runs normally | Both the remote and set mounted RUN lamps do not light, although the starter has disconnected normally and the engine is running. | Press the panel Lamp Test switch and replace the run lamp bulb if it does not light. Test the remote RUN lamp by suitable means and replace it if it does not light; If both lamps are good, this indicates that the AC disconnect circuit is not working. Check the AC voltmeter to determine whether or not there is generator output voltage and service as necessary. See There Is No Output Voltage in Troubleshooting; If there is generator output voltage, check for 120 VAC across pin connectors P1-1 and P1-2 on the ECM. If there is no voltage, check for loose or missing leads between the connectors and TB21-21 and TB21-32 inside the control box and service as necessary; Replace the ECM if there is 120 VAC across pin connectors P1-1 and P1-2 but neither RUN lamp lights during normal operation. |
| No output voltage | The line circuit breaker is OFF. | Find out why the circuit breaker was turned OFF, make sure it is safe to reconnect power, and then throw the circuit breaker ON. |
| No output voltage | The line circuit breaker has TRIPPED. | Shut down the set and service as necessary to clear the short circuit or ground fault that caused tripping, and then RESET the circuit breaker and start the set. |
| No output voltage | The line circuit breaker is faulty. | Shut down the set, make sure the power output lines from the set have been disconnected from all other sources of power, attempt to RESET the circuit breaker and throw it ON and check for electrical continuity across each line contact. Replace the circuit breaker if there is measurable resistance across any contact. |
| No output voltage | Voltage regulating faults (PMG-excited generators). | Follow the PMG test described in Section 5 to determine if it is okay; Check all connections against the applicable reconnection diagram (Section 8) and rewire as necessary. Replace the voltage regulator if the PMG checks okay, the wiring is correct and there is no output voltage. |
| No output voltage | Voltage regulating faults (Shunt-excited generators). | Flash the field as described in Section 5; Check all connections against the applicable reconnection diagram (Section 8) and rewire as necessary. Replace the voltage regulator if the wiring is correct and there is no output voltage. |
| No output voltage | The exciter field winding is open. | Shut down the set and check exciter field winding resistance according to Section 5. Replace the exciter field assembly if winding resistance does not meet specifications. |
| No output voltage | The rotating rectifier assembly (diodes CR1 through CR6) is faulty. | Shut down the set and check each diode according to Section 5. Service as necessary. |
| No output voltage | The exciter rotor windings are open. | Shut down the set and check exciter winding resistances according to Section 5. Replace the generator rotor assembly if exciter rotor winding resistances do not meet specifications. |
| No output voltage | The main rotor winding is open. | Shut down the set and check main rotor winding resistance according to Section 5. Replace the generator rotor assembly if main rotor winding resistance does not meet specifications. |
| No output voltage | The stator windings are open. | Shut down the set and check stator winding resistances according to Section 5. Replace the generator stator assembly if stator winding resistances do not meet specifications. |
| Output voltage is too high or too low | Engine speed is unstable. | Troubleshoot according to the chart, The Engine Lacks Power or is Unstable. |
| Output voltage is too high or too low | The voltage has been adjusted improperly. | Adjust output voltage according to Section 2, AC Control. |
| Output voltage is too high or too low | Improper connections have been made at the generator output terminals. | Shut down the set and reconnect according to the appropriate reconnection diagram. See Section 8. |
| Output voltage is too high or too low | The rotating rectifier assembly (diodes CR1 through CR6) is faulty. | Shut down the set and check each diode according to Section 5, Servicing the Generator. Service as necessary. |
| Output voltage is unstable | The voltage has been adjusted improperly. | Adjust output voltage according to Section 2, AC Control. |
| Output voltage is unstable | The voltage adjusting rheostat on the control panel is faulty (if provided). | Unlock the voltage adjusting screw on the front of the control panel and disconnect either lead from the rheostat. Measure resistance between terminals 1 and 2 while turning the adjusting screw fully one way and then the other. Replace the rheostat if it is open at any point, or if resistance does not vary smoothly from zero to approximately 1,500 ohms for sets with the SX460 voltage regulator (shunt excited) or 5,000 ohms for sets with the MX321 voltage regulator (PMG-excited). |
| The field circuit breaker keeps tripping | The rotating rectifier assembly (diodes CR1 through CR6) is faulty. | Shut down the set and check each diode according to Section 5. Service as necessary. |
| The field circuit breaker keeps tripping | The exciter field winding is shorted. | Shut down the set and check exciter field winding resistance according to Section 5. Replace the exciter field assembly if winding resistance does not meet specifications. |
| The field circuit breaker keeps tripping | The exciter rotor windings are shorted. | Shut down the set and check exciter winding resistances according to Section 5. Replace the generator rotor assembly if exciter rotor winding resistances do not meet specifications. |
| The field circuit breaker keeps tripping | The main rotor winding is shorted. | Shut down the set and check main rotor winding resistance according to Section 5. Replace the generator rotor assembly if main rotor winding resistance does not meet specifications. |
| The field circuit breaker keeps tripping | The stator windings are shorted. | Shut down the set and check stator winding resistances according to Section 5. Replace the generator stator assembly if stator winding resistances do not meet specifications. |
| The phase currents are unbalanced | The connected loads are distributed unevenly among the phases. | Shut down the set and redistribute the loads as evenly as possible. |
| The phase currents are unbalanced | Improper connections have been made at the generator output terminals. | Shut down the set and reconnect according to the reconnection diagram. See Section 8. |
| The phase currents are unbalanced | The stator windings are faulty (open or shorted). | Shut down the set and check stator winding resistances according to Section 5. Replace the generator stator assembly if stator winding resistances do not meet specifications. |
| The phase currents are unbalanced | A load has a ground fault or short circuit. | Service the faulty equipment as necessary. |
| Engine runs until fault shutdown due to overspeed | Overspeed module (PMG equipped sets) or overspeed switch cannot be adjusted; governor adjustment issue; linkage binding; speed pick-up unit output voltage less than 2.5 VDC; actuator unit does not drive the linkage through its full travel when power is connected or return it when power is disconnected; governor controller issues | Reset ECM, adjust governor, repair and adjust linkage as necessary, re-install magnetic speed pick-up unit to ensure correct clearance with flywheel gear teeth, replace speed-pickup unit if output voltage at cranking speed is less than 2.5 VDC, replace actuator or governor controller |
| Engine runs until fault shutdown due to low oil pressure | Check engine oil level, repair any oil leaks and fill to proper level; reset ECM if set still shuts down; service lubricating oil system according to engine service manual if oil pressure is less than 14 psi (97 kPa); replace low oil pressure cutout switch if oil pressure is greater than 14 psi (97 kPa) | |
| Engine runs until fault shutdown due to high engine temperature | Check engine coolant level, repair any coolant leaks and refill as necessary; reset ECM if set still shuts down; start engine and observe coolant temperature as system heats up; replace high engine temperature cutout switch if shutdown occurs before coolant reaches 230° F (110° C); clean and service cooling system as required to restore full cooling capacity | |
| Engine runs until fault shutdown due to fault indication switches | Service as required; if shutdown was due to low frequency, check for fuel supply or governor adjustment issues; if shutdown was due to over/under voltage, check voltage regulator |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: The line circuit breaker is OFF.; The line circuit breaker has TRIPPED.; The line circuit breaker is faulty.; Voltage regulating faults (PMG-excited generators).. See the table for the matching fixes.
Documented causes: The Emergency Stop switch has been used. (The switch button is lit.); A Fault Shutdown is being indicated by one of the red lights on the control panel.; A LO Shutdown is being indicated on the day tank pump control panel.; Cranking voltage is too low to crank the engine.. See the table for the matching fixes.
Documented causes: Fuel delivery to the genset is inadequate.; The fuel is contaminated.; The engine air filter element is dirty.; The governor settings or linkage adjustment is incorrect.. See the table for the matching fixes.