Controller shows E03 and the generator will not crank when AUTO or MANUAL start is requested.

Safety first: Ensure the generator is in OFF mode and all AC loads are disconnected. Wear eye protection when working around batteries.

• Inspect battery connections: Remove the battery cover. Check that the positive and negative terminals are tight and free of corrosion. Clean corrosion with a mixture of baking soda and water, then rinse and dry. Re‑tighten terminals.
• Measure battery voltage: Use a multimeter set to DC volts. A healthy fully charged 12V battery should read about 12.6–12.8V with the engine off. If below 12.0V, the battery is significantly discharged.
• Charge or replace battery: Disconnect the battery and charge it with an external smart charger until full. If the battery will not hold a charge or is more than 4–5 years old, replace it with a DuroStar‑approved starting battery of the same group size and CCA rating.
• Check built‑in charger: With AC utility power present, measure voltage at the battery terminals; it should be around 13.2–13.6V if the onboard charger is working. If voltage does not rise above static battery voltage, test the DuroStar battery charger module and replace if faulty.
• Inspect ground cable: Verify the negative cable from the battery to the generator frame is tight and free of paint or rust at the contact point. Clean and re‑secure if needed.
• Clear code and test: After correcting issues, clear E03 on the controller (if applicable) and attempt a manual start. If the code reappears with a known good battery and charger, have a technician test the control board's charging circuit.