Generator attempts to start but stops and shows E03 on the display.

Safety first: Switch the generator to OFF, disconnect battery negative, and prevent auto-start. Overspeed conditions are dangerous; do not repeatedly attempt to start until inspected.

• Inspect throttle and governor linkage: Manually move the throttle lever on the carburetor or injection pump. It should move smoothly and return via the governor spring. Clean any corrosion, remove debris, and lubricate pivot points lightly.
• Check speed sensor: Locate the engine speed sensor (often a magnetic pickup near the flywheel or ring gear). Inspect the connector and wiring harness for damage. Ensure the sensor tip is clean and set to the specified gap from the target wheel (refer to Yamaha spec, typically around 0.5–1.0 mm).
• Inspect governor module connections: Verify tight, clean connections at the electronic governor actuator and the governor control module. Look for burnt smell or discoloration indicating overheating.
• Controller frequency feedback: Confirm that the AC output wiring to the controller (used for frequency sensing) is intact and not loose at the terminal block. Loose connections can cause false overspeed detection.
• Test run: Reconnect the battery, clear the code, and start the generator while monitoring engine speed and frequency with a meter. If the engine truly races, shut down immediately and have a Yamaha technician inspect the governor system.