Generator will not start and control panel displays E01 immediately after crank attempt.

Safety first: Turn the generator to OFF, disconnect the battery negative cable, and ensure the unit cannot auto-start. Allow the engine to cool fully before working on it.

• Check oil level: Remove the dipstick, wipe it, reinsert fully, then check the level. Top up with the Yamaha-specified engine oil grade to the FULL mark. Do not overfill.
• Inspect for leaks: Look around the oil filter, drain plug, crankcase gasket, and oil cooler lines for wet oil. Tighten fittings or replace gaskets as needed.
• Reset and test: Reconnect the battery, clear the code per the Yamaha controller instructions (usually by switching to OFF/RESET, then back to AUTO), and attempt a start. If E01 returns immediately, continue.
• Test oil pressure switch: Locate the oil pressure switch on the engine block. Disconnect its connector and check for continuity to ground with the engine off (most low-oil switches are normally closed to ground). If it is open or shorted incorrectly, replace the switch.
• Inspect wiring: Trace the harness from the oil pressure switch to the control module. Look for chafed insulation, corrosion at connectors, or loose pins. Repair or replace damaged wiring.
• If still no start: Actual low oil pressure or internal engine damage may be present. Do not bypass the switch. Contact a Yamaha-authorized service technician for oil pressure testing with a mechanical gauge.