So I have a 24' Kubota L2502, manual 4 speed with a loader and hoe on it. I was running it last week and digging out my leech field, when it suddenly stopped running with an audible alarm/beep. That beep or tone was a second or two long and replicated every time I turned the key from off to on. This tone is not something that is ever present normally. When i would turn to crank I got nothing. Dealer said it was a sensor. All sensors were checked, the PTO sensors was cracked so I bridged it. Still no joy. I ended up having a neighbor use his slightly smaller machine to tow me out of the hole, down the side of the mountain (in SW Colorado) and up on to the trailer. All in all, a 3 hour adventure or chore. I took it down to the dealer and even though on the phone I had asked about fuses or relays - and they had said there were none - the first thing the tech checked was the fuse box. Guess what, it was a fuse for the sensors which had blown, probably due to the bad PTO sensor. They gave me a new fuse and a new sensor and it fired right up. They never even pulled it off the trailer. I'm posting in case someone else has a USA L series that won't start and is getting that tone. After you check your sensors, check the fuse labeled sensor. Hopefully it will save you the headache of towing your machine!