error 54

1. If iTunes is already open, quit and reopen it.
2. Check your third-party security software.
3. Make sure that your USB cable, computer, and network are reliable.
4. Check for outdated or modified software. 

If you still see the error, contact Apple Support.

Actually it can also be one from iTunes that was purchased if there was an issue with downloading it. I would start with temporarily closing down all the security I suggested and see if it works. If not, try syncing just one song after you play it on your computer and see if it works (all the way through). After that it is a matter or selecting more songs until you run into the error again. Then look at just the material that was added since the last song to try to locate the offender. Before doing that you might want to scan the file size of your media and see if there are any that are far, far larger than they should be or is a 0K file.

If you see error -54 when you sync with your computer - Apple Support

I would suspect in that case that it is a problem on your computer, what make/model and OS is it? You tried to temporarily disable ALL of your antivirus/antispyware/malware and security software?

I'm taking it that you don't have a lot of technology skills or familiarity with syncing.

If you follow what I said you since 1 song first just to make sure it is working and you do not get an error.

After that select 100 songs and try syncing them. If it works and you don't get an error move on to the next 100, etc. Once you hit the error you have 100 songs to look at and try to figure out which song (or songs) have the problem. You can look at them first in your library and see if the file size on some looks odd, as I said before, and try unchecking those and don't sync them.

This used to be a more prevalent problem because of music piracy and people would add music from torrent sites that were botched. Or they were copying CDs from someone and there was an error in ripping an album.

If you aren't up to this find a friend who is really good with Apple products and pay her 50 bucks to fix this for you.

I didn’t say that so I don’t know where you are reading that.

Where in that statement does it say to erase anything?

Was that ALL of your antivirus/antimalware software?