Cummins/Onan HDZAA troubleshooting: 39 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan HDZAA — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Remedy |
|---|---|---|
| OVER TEMPERATURE (INVERTER) | Inverter temperature detected to be over 70°C | Reduce loads, verify heat sink cleanliness and air flow; if issue persists after cooling, replace inverter |
| OVERLOAD | Too many applications connected or inverter defective | Measure current draw, reduce loads, test with load bank, check stator and replace if necessary; perform stator check before replacement |
| Symptom | Cause | Remedy |
|---|---|---|
| The Operator Panel in the vehicle must be able to communicate with the inverter in the generator set. If communication is interrupted this fault will likely occur when attempting to start the generator set. | 1. The Operator Panel in the vehicle must be able to communicate with the inverter in the generator set. If communication is interrupted this fault will likely occur when attempting to start the generator set. 2. Without power from the PMA auxiliary windings AC3 and AC4, the inverter will not be able to communicate with the Operator Panel. If the output frequency detected by the inverter is too high (engine speed greater than 4200rpm) the inverter will shut down the generator set. See PMA information in section 4−9 for engine speed calculation. 3. Faulty inverter. | 1. Disconnect the vehicle AC wiring from the generator set and connect the generator set to a load bank. If the problem goes away check the vehicle AC wiring for shorts. Shorts to ground can cause an inverter communications fault. 2. Check for open wiring, shorts to ground, and bad crimps at the 2-pin connector on the inverter and at Pins 1 and 6 of the 6-pin connector on the internal control board. 3. Check for open wiring to ground and bad crimps at Pin 5 of the 6-pin connector on the internal control board. 4. Check for open wiring, shorts to ground, and bad crimps at Pins 1 and 4 of the 12-pin connector on the Operator Panel and for good connections at pins 7 and 10 of the 10-pin connector on the internal control board. 5. Check for open wiring, shorts to ground, and bad crimps at Pins 4 and 9 of the 9-pin connector on the inverter. 6. Check PMA winding connections to the internal control board and inverter. Refer to PMA tests (p. 4-9) and replace PMA stator if necessary. 7. Replace a faulty inverter. |
| Inverter temperature detected to be over 70 C. | 1. Reduce loads. 2. Verify that the inverter heat sink is clean and that there is no air flow restriction or hot air recirculation. 3. After allowing generator and inverter too cool, start and run the generator set with no load. If it still shuts down on OVER TEMPERATURE, replace the inverter. | |
| Too many applications are connected, or the inverter is defective. | 1. Measure current draw. If it is greater than 32 amps, reduce the number of appliances connected in the coach and wait a few minutes for generator set to cool down. Press STOP to stop engine and restart the generator set. 2. If the generator set shuts down on ’Overload’ condition, disconnect it from the coach and bench-test with a load-bank. If the generator set runs fine without shutting down, then the problem likely exists within vehicle wiring and/or appliances. In the event that it shuts down with no load connected, perform checks in Step 3. 3. Ensure stator is not damaged and has no shorts internally or to Ground on all Main and Auxiliary Windings. Test winding insulation resistance with a Megger. Replace state if necessary. If the stator is good, replace the inverter. | |
| Engine speed is below 2300 rpm | 1. Check that the engine stop lever is in its vertical (run) position (Figure 5-1). Refer to Engine Workshop Manual 983−0504 if the lever does not return to the run position after it has been pushed to stop the engine. 2. Reduce Loads: Disconnect AC output leads and connect to load bank. Test performance. 3. Check Fuel Flow: Verify fuel flow from lift pump it should be approximately 0.4 pints/min (200 ml/minute) If flow is low check for kinked hoses and replace fuel filter as needed. 4. Check air flow (intake, exhaust) for restrictions: Remove exhaust and test, (spark arrestor clean out may be needed). 5. Verify that the stop solenoid is operating correctly. Replace the solenoid if it does not pull in when 12 VDC is applied to its terminals. 6. Check the PMA winding connections at the internal control board and inverter. Refer to PMA tests (p. 4-9). Replace PMA stator if necessary. 7. The engine “wet-stacked” when run under no load. Run under approximately 3/4 rated load for approximately 30 minutes. If the problem persists, go to Step 8. 8. The injector is partially blocked. Check the spray pattern and replace as necessary. Refer to Engine Workshop Manual 983−0504. 9. The injector popping pressure is too Low. Check the popping pressure and replace as necessary. Refer to Engine Workshop Manual 983−0504. 10. The engine is worn. Refer to Engine Workshop Manual 983−0504. | |
| Gen Wait should appear on the display. | Clear the Gen Wait message from the Operator Panel by cycling it off and on. Try starting again. | |
| Engine cranks but does not start. | Possible Cause/Diagnosis/Repair | 1. Clear the Gen Wait message from the Operator Panel by cycling it off and on. Try starting again. 2. Check the fuel level and fill as necessary. 3. Press the stop switch (p. 2-2) if it is not in its “1” position. 4. Replace the fuel if it is not of the specified grade or suitable for the ambient temperature (p 2-1). 5. Check Fuel flow from lift pump, should be approximately 0.4 pints/minute (200 ml/minute). Look for kinked hoses and replace fuel filter as need. 6. Verify that the fuel solenoid is getting 12V DC and clicks open when energized. 7. The cam to crank timing is off. Check Timing. Refer to Engine Workshop Manual 983−0504. 8. Valves not set properly: Check Valve lash. Refer to Engine Workshop Manual 983−0504. 9. The injector nozzle is blocked or locked. Remove the injector and check popping pressure and spray pattern. Refer to Engine Workshop Manual 983−0504. 10. The injection pump is stuck. Remove the high pressure injector line and crank the engine. Watch for fuel at delivery valve. Refer to Engine Workshop Manual 983−0504 11. Engine compression is low—blown head gasket, bad injector seal, worn engine. Refer to Engine Workshop Manual 983−0504. |
| Engine spits/sputters/exhausts white smoke. | Possible Cause/Diagnosis/Repair | 1. Air in fuel system: Prime fuel system by turning on the display, lift pump should run for 5 minutes to prime system. If problem goes away check for air leaks with soapy water at fittings and hoses. |
| Engine exhausts black smoke. | Possible Cause/Diagnosis/Repair | 1. The injector is partially blocked. Check the spray pattern and replace as necessary. Refer to Engine Workshop Manual 983−0504. 2. The injector popping pressure is too Low. Check the popping pressure and replace as necessary. Refer to Engine Workshop Manual 983−0504. |
| Engine won’t stop. | 1. Stop the engine by pushing the engine stop lever (Figure 5-1) all the way to the left. 2. Remove the fuel solenoid and apply 12V DC. Replace the solenoid if it does not function (click open). 3. Contact HATZ to readjust the idle adjustment screw. | |
| Inverter communications fault | Shorts to ground in vehicle AC wiring | Check the vehicle AC wiring for shorts |
| Open wiring, shorts to ground, or bad crimps at specified connectors | Check 2-pin connector on inverter and Pins 1 and 6 of the 6-pin connector on internal control board | |
| Open wiring to ground or bad crimps at Pin 5 of the 6-pin connector | Check Pin 5 of the 6-pin connector on internal control board | |
| Open wiring, shorts to ground, or bad crimps | Check Pins 4 and 9 of the 9-pin connector on inverter | |
| PMA winding connections to internal control board and inverter | Refer to PMA tests and replace PMA stator if necessary | |
| Inverter fault | Replace a faulty inverter; perform stator check before replacement | |
| Engine speed below 2300 rpm | Apply derates for elevation and temperature, reduce loads, test with load bank, check fuel flow, air flow, stop solenoid operation, PMA connections; run under load if necessary, check injector spray pattern and popping pressure, engine wear | |
| Dead operator panel | Verify battery charge, check 12 VDC at specified pins, replace 30 amp fuse if blown, check internal control board and Operator Panel as necessary | |
| Engine cranks but does not start | Clear Gen Wait message from Operator Panel by cycling it off | |
| LOW BATTERY | Battery voltage is below the minimum value (9 VDC) necessary to start the generator set. | Check battery connections and recharge or replace the battery. |
| OIL CHANGE / CHECK OIL LEVEL | These messages appear every time the generator set hour counter reaches preset oil check/change intervals (check every 20 hours and then change the oil the first time at 50 hours and then every 250 hours). The generator set continues to run. Fill or change oil as necessary. The generator set must be running to reset the message. Hold START (green button) until the message clears. If not reset, the message will reappear after an hour of running. | |
| SHORT CIRCUIT | A connected appliance probably has a short circuit. | AC output voltage is turned off but the engine is kept running to cool the generator set. Disconnect all appliances, press STOP to stop the engine and then restart the generator set. Reconnect appliances one by one to find out which one shorted and have it repaired or replaced. |
| OIL TEMP-PRESS | The engine lubricating oil temperature is too high or the pressure is too low. The oil pressure and temperature switches are connected in parallel. | Diagnosis/Repair—Low Oil Pressure: 1. Check Oil level and refill as necessary. 2. The oil pressure switch is normally closed (closes between 2.5 and 3.6 psi). Normal pressure is 36 psi at 3100 RPM. With the engine stopped, check for continuity to ground through the oil pressure switch. Replace if open. 3. If the oil pressure switch is opening, verify the connections between the engine harness and internal control board. Check for shorts to ground. To check if the switch is opening remove wire No. 4 (black) from the engine harness connector on the engine side of the connector. Start the generator set and verify that the switch is opening. If this test is performed without removing the wire from the harness, the test meter may provide enough of a ground path to shut down the generator set. 4. If the switch does not open, one of 3 conditions exists: a) short to ground in the engine harness, b) faulty oil pressure switch, c) low engine oil pressure. Remove the oil pressure switch and test operation using a hand pump to apply appropriate pressure. Check harness for shorts to ground. Replace wiring and or switch as necessary. If the oil pressure circuit is okay, check the high oil temperature protection circuit. |
| GENERATOR ALERT | There are three possible causes: 1. The Operator Panel in the vehicle must be able to communicate with the inverter in the generator set. If communication is interrupted this fault will likely occur when attempting to start the generator set. 2. Without power from the PMA auxiliary windings AC3 and AC4, the inverter will not be able to communicate with the Operator Panel. If the output frequency detected by the inverter is too high (engine speed greater than 4200rpm) the inverter will shut down the generator set. See PMA information in section 4−9 for engine speed calculation. 3. Faulty inverter. | CAUTION Always perform stator check before replacing the invertor. Failure to do so will result in damage to the inverter. |
| Exhaust leaks at every startup and after every eight hours of running. | Inspect for exhaust leaks. | |
| Operating the generator set when parked in a confined space such as a garage. | Do not operate the generator set in a confined space. | |
| Exhaust system not installed according to the generator set Installation Manual. | The exhaust system must be installed in accordance with the generator set Installation Manual. | |
| Engine cooling air used for heating the vehicle. | Engine cooling air must not be used for heating the vehicle. | |
| Generator electrical output connections made by an untrained or inexperienced electrician. | Generator electrical output connections must be made by a trained and experienced electrician in accordance with applicable codes. | |
| Generator set connected to shore power (utility) without an approved switching device. | The generator set must not be connected to shore power. An approved switching device must be used to prevent interconnections. | |
| Working on live electrical equipment without caution. | Use caution when working on live electrical equipment. Remove jewelry, make sure clothing and shoes are dry, stand on a dry wooden platform or rubber insulating mat and use tools with insulated handles. | |
| Working in areas sharing ventilation with fuel tanks or equipment. | Keep flames, sparks, pilot lights, arc-producing equipment and all other sources of ignition well away. | |
| OVER TEMPERATURE (INVERTER) | Inverter temperature detected to be over 70° C. | Reduce loads. |
| OVERLOAD | Too many applications are connected, or the inverter is defective. | 1. Measure current draw. If it is greater than 32 amps, reduce the number of appliances connected in the coach and wait a few minutes for generator set to cool down. Press STOP to stop engine and restart the generator set. 2. If the generator set shuts down on 'Overload' condition, disconnect it from the coach and bench-test with a load-bank. If the generator set runs fine without shutting down, then the problem likely exists within vehicle wiring and/or appliances. In the event that it shuts down with no load connected, perform checks in Step 3. 3. Ensure stator is not damaged and has no shorts internally or to Ground on all Main and Auxiliary Windings. Test winding insulation resistance with a Megger. Replace state if necessary. If the stator is good, replace the inverter. |
| LOW ENGINE POWER | Engine speed is below 2300 rpm | Contact an authorized Cummins Onan dealer. |
| ENGINE SPITS/SPUTTERS/EXHAUSTS WHITE SMOKE | 1. Air in fuel system: Prime fuel system by turning on the display, lift pump should run for 5 minutes to prime system. If problem goes away check for air leaks with soapy water at fittings and hoses. | |
| ENGINE EXHAUSTS BLACK SMOKE | Contact an authorized Cummins Onan dealer. | |
| ENGINE WON’T STOP | Contact an authorized Cummins Onan dealer. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: 1. The Operator Panel in the vehicle must be able to communicate with the inverter in the generator set. If communication is interrupted this fault will likely occur when attempting to start the generator set. 2. Without power from the PMA auxiliary windings AC3 and AC4, the inverter will not be able to communicate with the Operator Panel. If the output frequency detected by the inverter is too high (engine speed greater than 4200rpm) the inverter will shut down the generator set. See PMA information in section 4−9 for engine speed calculation. 3. Faulty inverter.. See the table for the matching fixes.
Documented causes: Possible Cause/Diagnosis/Repair. See the table for the matching fixes.
Documented causes: Possible Cause/Diagnosis/Repair. See the table for the matching fixes.