DIAGNOSIS E02 is an over-speed error. The engine is running too fast, and the inverter board has shut down output to protect your electronics.
FIX The most common cause is a dirty or faulty throttle body. Engine can't regulate speed properly. Turn generator off. Remove the air filter cover and filter. Spray carburetor cleaner directly into the throttle body bore while working the throttle linkage by hand. Let it sit for 10 minutes, reassemble, and try.
IF THAT DIDN'T WORK The stepper motor that controls the throttle plate might be faulty. It's mounted on the throttle body. You'll need a multimeter to test its resistance.
HEADS UP Running with an E02 fault can damage sensitive electronics you have plugged in. Do not attempt to bypass this error. Fix the root cause.