I was given a TS-440 that was lightly used. Being old it does need some work. This week I am doing the "Button Bounce" fix. Several of the buttons were bouncing so I pulled the component and cleaned up the pads and disks, then remounted them. All work well except the scan button. When I press it and release I get three quick beeps. If I press and hold it I get one beep on the press and three on the release. It did this when I got the rig and fixing the bounce problem did not change it. I know this is not likely to be the pad or disk as I did them all at once the exact same way. Does anybody know what this might be? Besides frustrating.
Have you tried this in memory, program, and vfo mode? If there are no memories saved, it may squawk at you because there's nothing to scan. I suspect it will do the same if you try to scan in 'program' mode without the lower and upper frequency limits saved in memory channels 6 and 7 respectively for PG.S-1 and 8 and 9 for PG.S-2, though the manual doesn't say that for sure.
I would think they would program something generic in to the memories at the factory so that the scan function works right out of the box, but I'm not sure about that. It's also possible that the program scan channels aren't protected and an MCU reset at some point in the past cleared them as well.
The manual doesn't say anything at all about it having an unbounded VFO mode scan, so the beeps might just mean "That doesn't exist".
Here's a link to the manual in case you don't have one, the bit you want is on Pages 17 and 18.