Cummins/Onan DFAA troubleshooting: 26 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan DFAA — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Remedy |
|---|---|---|
| FAULT 1 or 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. |
| FAULT 1 or FAULT 2 | The FAULT 1 or FAULT 2 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.) |
| Symptom | Cause | Remedy |
|---|---|---|
| Green RUN lamp lights following engine startup. | Indicates all engine systems are normal. No corrective action required. | |
| PREHI ENGINE TEMP lamplights. Engine continues to operate. | Indicates engine has begun to overheat and engine temperature has risen to approximately 215°F (102°C) or coolant level is low on optionally wired sets. 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. if engine can be stopped, follow procedure in step 3. | |
| HI ENG TEMP lamp lights. Engine shuts down. | Indicates engine has overheated (engine temperature has risen above 222°F/106°C) or coolant level is low. Allow engine to cool down completely before proceeding with the following checks: a. Check coolant level and replenish if low. Look for possible coolant leakage points and repair if necessary. b. Check for obstructions to cooling airflow and correct as necessary. c. Check for a slipping fan belt and tighten if loose. d. Reset control and restart after locating and correcting problem. Contact an authorized service center if none of the above. | |
| PRELO OIL PRES lamp lights. Engine continues to operate. | Indicates 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 foliow step 5 procedure. If engine can be stopped, follow procedures in step 5. | |
| LOOIL PRES lamp lights. Engine shuts down. | Indicates 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. | A. Check for empty fuel tank, fuel leaks, or plugged or fuel lines and correct as required. Engine runs, shuts down, and LO OIL 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. | 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. | |
| 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 ENGINE CRANKS BUT DOES NOT START | The engine is not getting fuel, Fuse F2 on the engine monitor board A11 has blown, Fuel solenoid K1 does not energize, Low engine temperature is causing too low a cranking speed for starting, Cranking voltage is too low to reach required cranking speed, The air cleaner is blocked, Ignition system, fuel system or other engine malfunction | Open any closed shutoff valve. Fill the main fuel supply tank., Replace fuse with one of the same type and amp rating. If fuse F2 blows again, the wire between A11 TB1-10 and engine block terminal T26, or the wire between T26 and fuel solenoid K1 may be loose or shorting to ground., a. Fuel solenoid not energized by ECM A11. Check for B+ at TB1-10 when cranking. If no voltage present and fuse F2 is good replace ECM. b 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., a. Plug in, repair or install engine coolant and engine oil heaters. b. Replace the engine oil if it is not of the recommended viscosity for the ambient temperature., a. 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. b. Recharge or replace the battery. Specific gravity for a fully charged battery is approximately 1.260 at 80° F (27° C). c. Replace the engine-driven battery charging alternator if normal battery charging voltage is not between 24 and 28 volts., Service as necessary., Service according to the engine service manual. |
| THE ENGINE RUNS UNTIL FAULT SHUTDOWN | The OVERSPEED lamp comes on when the engine shuts down, The LO OIL PRES lamp comes on when the engine shuts down, The HI ENG TEMP lamp comes on when the engine shuts down, The FAULT 1 or FAULT 2 lamp comes on when the engine shuts down | A. Reset engine monitor board A11 by pushing the Run-Stop-Remote switch to Stop and the Reset switch to Reset and restart the set, monitoring engine speed and adjust the Electronic Overspeed Module (Section 3). b. Check the governor for binding, repair and adjust the governor as necessary (see Section 6). a. Check the engine oil level, repair any oil leaks and fill to the proper level. Then reset engine monitor board A11 by pushing the Run-Stop-Remote switch to Stop and the Reset switch to Reset. b. 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 10 psi. Replace the low oil pressure cutout switch if oil pressure is greater than 10 psi. See Section 8 to locate the switch. a. Check the engine coolant level, repair any coolant leaks and refill as necessary. Then reset engine monitor board A11 by pushing the Run-Stop-Remote switch to Stop and the Reset switch to Reset. b. 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 200° F (93° C), replace the high engine temperature cutout switch. If coolant temperature exceeds 200° F (93° C), clean and service the entire cooling system as required to restore full cooling capacity. See Section 8 to locate the switch. 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, The fuel is contaminated | A. Check for clogged fuel lines and filters. b. Check for air in the fuel lines and repair all air leaks. c. Measure the vertical distance between the fuel lift pump on the engine and bottom of the dip tube in the supply tank. The lift must not exceed 6 feet (1.8 meters). Connect the set to a supply of good quality fuel and |
| The PRE LO OIL PRES lamp comes on while the engine is running. | Oil pressure will be less than 20 psi but greater than 14 psi. | Shut down the set if possible or disconnect non-critical loads. Service the engine lubricating system according to the engine service manual. |
| The PRE HI ENG TEMP lamp comes on while the engine is running. | Engine temperature will be greater than 220°F but less than 230° F. | Shut down the set if possible or disconnect non-critical loads. Service the engine cooling system to restore full cooling capacity. |
| The LOW ENGINE TEMPERATURE lamp comes on while the set is in standby. | A. Plug in, repair or install engine coolant and engine oil heaters. b. If the engine coolant gauge indicates more than 70° F (21°C), replace the gauge board. See Figure 3-4. | |
| 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.) | |
| THE GREEN RUN LAMP STAYS OFF BUT THE SET RUNS NORMALLY | A. Press the panel Lamp Test switch and replace the run lamp bulb if it does not light. b. If the lamp is good and the set has an older ECM board (one with cartridge-type fuses), this indicates that the DC disconnect circuit (K14 relay on ECM) is not working. Check the DC voltmeter and if there is not at least 24 VDC, check for loose or missing wiring between the battery charging alternator terminal TB1-2 and pin connector P1-3 on the ECM. See the connection diagram in Section 8. If the connections are good replace the battery charging alternator. c. If the RUN lamp, wiring connections and battery charging alternator are all good and the RUN lamp does not light, replace the engine monitor board A11. | |
| Both the remote and set mounted RUN lamps do not light, although the starter has disconnected normally and the engine is running. | A. 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. b. 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. c. If there is generator output voltage, check for 120 VAC across pin connectors P1-1 and P1-2 on engine monitor board A11. 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. d. Replace engine monitor board A11 if there is 120 VAC across pin connectors P1-1 and P1-2 but neither RUN lamp lights during normal operation. | |
| NO OUTPUT VOLTAGE | 1. 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. 2. 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. 3. 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 | |
| Field circuit breaker CB21 has TRIPPED. | RESET the circuit breaker. If it keeps tripping, troubleshoot according to the chart, Field Circuit Breaker Keeps Tripping. | |
| 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. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: The engine is not getting fuel, Fuse F2 on the engine monitor board A11 has blown, Fuel solenoid K1 does not energize, Low engine temperature is causing too low a cranking speed for starting, Cranking voltage is too low to reach required cranking speed, The air cleaner is blocked, Ignition system, fuel system or other engine malfunction. See the table for the matching fixes.
Documented causes: The OVERSPEED lamp comes on when the engine shuts down, The LO OIL PRES lamp comes on when the engine shuts down, The HI ENG TEMP lamp comes on when the engine shuts down, The FAULT 1 or FAULT 2 lamp comes on when the engine shuts down. See the table for the matching fixes.
Documented causes: Fuel delivery to the genset is inadequate, The fuel is contaminated. See the table for the matching fixes.