Ryobi standby generator shuts down during operation and displays E04 on the controller.

Safety first: Place the generator in OFF mode, disconnect the battery negative cable, and wait for all moving parts to stop.

• Check and replace air filter: Open the air filter housing. Remove the filter element and inspect for heavy dirt or oil saturation. Replace with a genuine Ryobi air filter if dirty. Do not run without a filter.
• Inspect governor and throttle movement: With the engine off, move the throttle lever and governor arm by hand. They should move freely. Clean any debris or corrosion from pivot points and linkages.
• Reduce electrical load: Verify that the automatic transfer switch (ATS) is not feeding more circuits than the generator is rated for. Temporarily turn off high‑demand loads (HVAC, electric water heater) at the main panel and retest. Persistent underspeed under normal load suggests a fuel or engine issue.
• Clean carburetor (intermediate skill): Shut off fuel supply. Remove the carburetor bowl and clean jets with carburetor cleaner and compressed air. Reassemble with a new bowl gasket if damaged.
• Reset and test: Restore fuel, reconnect the battery, clear E04, and start the generator with minimal load. If RPM remains low or the code returns, have a technician check fuel pressure, compression, and governor adjustment.