Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Hello, my name is ***** ***** I am going to assis you with this.
"US" means Under Speed. It means that the controller is sensing that the engine is not running fast enough.
Possible causes of this are:
Sticking/binding throttle linkage
Bad stepper motor (throttle controller)
Bad control board
Fuel supply issues
Too much load on the genset