Cummins/Onan 2.5 EGHAA troubleshooting: 30 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan 2.5 EGHAA — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Cause | Remedy |
|---|---|---|
| FAILS TO CRANK (ELECTRIC START MODELS) | Low Battery, Bad battery connection, Oil is too heavy, Load is connected | Check battery electrolyte level and charge. Clean and tighten all battery and cable connections. Replace with lighter oil. Always disconnect load while starting. |
| CRANKS SLOWLY (ELECTRIC START MODELS) | Choke closed, Dirty air filter, Rich fuel mixture | Open choke. Clean or replace air filter. Contact an Onan service center. |
| ENGINE WONT START | Loose or worn spark plug lead, Faulty spark plug, Dirty fuel filter or generator set at too steep of an angle, Governor out of adjustment or lean fuel mix | Check spark plug lead connection. Remove and clean or replace spark plug. Check fuel filter and generator set angle. Contact an Onan service center. |
| EXHAUSTING BLACK SMOKE | Open DC circuit breaker due to an overload | Remove all loads, reset circuit breaker, check for an overload or short circuit. Do not exceed generator set rated load specifications. |
| UNIT RUNS THEN STOPS | Add fuel. Add oil. Reduce oil level. | |
| UNIT RUNS BUT SURGES | Add fuel. Add oil. Reduce oil level. | |
| NO AC OUTPUT VOLTAGE | Open AC circuit breaker due to an overload | Remove all loads, re-set circuit breaker, check tools or appliances being used for defects. Do not exceed generator set rated load specifications. |
| Engine misfires | Worn or fouled spark plug | Clean or replace spark plug |
| Lean fuel mixture | Incorrectly adjusted carburetor | See Carburetor Adjustment section |
| Contaminated fuel | Drain fuel tank and refill with fresh fuel | |
| Dirty air cleaner | Clean or replace air cleaner | |
| Backfires | Worn or fouled spark plug | Clean or replace spark plug |
| Excessive engine wear | E140H engine: See Onan Elite Horizontal engine manual 965-0758 GH170, GH280 engines: See Engine Block Assembly section | |
| Restricted fuel flow | Plugged fuel filter | Clean or replace fuel filter |
| Incorrect fuel mixture | Incorrectly adjusted carburetor | See Carburetor Adjustment section |
| Exhaust system blocked or restricted | Locate and remove cause of blockage | |
| Incorrect valve clearance or defective valve(s) | E140H engine: See Onan Elite Horizontal engine manual 965-0758 GH170, GH280 engines: See Engine Block Assembly section | |
| No load speed set too low | Adjust governor setting | |
| Excessive engine wear or damage to engine | E140H engine: See Onan Elite Horizontal engine manual 965-0758 GH170, GH280 engines: See Engine Block Assembly section | |
| Restricted air flow | Dirt or debris blocking air inlet or outlet | Clear away any debris that may restrict airflow |
| Dirt or oil covering engine cooling fins | Clean away all dirt and oil from engine cooling fins | |
| Cooling fan plugged or broken | Inspect cooling fan, see Generator Service section | |
| Clogged or faulty breather | Clean or replace breather | |
| Black exhaust smoke | Dirty air cleaner | Clean or replace air cleaner |
| White or blue exhaust smoke | Dirty air cleaner | Clean or replace air cleaner |
| FAILS TO CRANK | 1. Low battery. 2. Bad battery connection. | 1. Check battery electrolyte level. 2. Clean and tighten all battery and cable connections. |
| CRANKS SLOWLY | 1. Low battery. 2. Bad battery connection. | 1. Check battery electrolyte level. 2. Clean and tighten all battery and cable connections. |
| ENGINE WON’T START | 1. Fuel below genset pickup level in tank. 2. Fuel supply shutoff valve closed. 3. Remove spark plug and clean. 4. Add oil if necessary. | 1. Add fuel. 2. Fully open fuel supply valve. 3. Replace with recommended oil. 4. Disconnect load while starting. |
| UNIT RUNS THEN SURGES | 1. Loose or worn spark plug lead 2. Faulty spark plug. 3. Dirty fuel filter or generator set at too steep of an angle. 4. Governor out of adjustment or lean fuel mixture. | 1. Check spark plug lead connection. 2. Remove and clean or replace. 3. Check fuel filter and angle of generator set. 4. Contact an Onan service center. |
| NO DC OUTPUT VOLTAGE | 1. Open DC circuit breaker due to an overload. | 1. Remove all loads, reset breaker, check for shorted battery or load defects. Do not exceed rated load specifications. |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Low Battery, Bad battery connection, Oil is too heavy, Load is connected. See the table for the matching fixes.
Documented causes: Choke closed, Dirty air filter, Rich fuel mixture. See the table for the matching fixes.
Documented causes: Loose or worn spark plug lead, Faulty spark plug, Dirty fuel filter or generator set at too steep of an angle, Governor out of adjustment or lean fuel mix. See the table for the matching fixes.