Generator shuts down shortly after starting and displays E02 on the Firman controller.

Safety first: Turn the generator OFF and disconnect the battery negative cable. Allow the engine to cool completely (at least 30–45 minutes). Never open a hot radiator cap.

• Check coolant level (liquid-cooled Firman standby models): Remove the radiator cap only when cool. Coolant should be near the neck. Top up with the coolant type specified by Firman (usually a 50/50 premix). Also check the overflow reservoir level.
• Inspect for coolant leaks: Look around radiator hoses, water pump, thermostat housing, and radiator core for dried coolant residue or wet spots. Tighten clamps or replace hoses as needed.
• Clean radiator and cooling fins: Use compressed air from the inside out to blow debris from the radiator core and any engine shrouds. Remove leaves, dust, and insects from the air intake grills and louvers of the Firman enclosure.
• Check cooling fan operation: On restart, observe whether the electric cooling fan (or belt-driven fan) runs. If the fan does not run, test the fan motor, fan relay, and associated fuse. Replace the fan assembly if seized or inoperative.
• Inspect temperature sensor and wiring: Locate the engine coolant temperature sensor on the cylinder head or thermostat housing. Check the connector for corrosion and ensure the harness to the control board is intact. Replace the sensor if resistance readings are out of spec per the service manual.

If E02 recurs despite proper cooling system function, a technician should test the thermostat, water pump flow, and verify the controller's temperature input.