iPod classic 240gb won't sync with iTunes 12

If iTunes on a Windows PC can access the iPod, does that mean it is formatted for PC (not Mac)? In other words, was the last Restore (for that iPod) done using iTunes on the Windows PC? If it is currently formatted for Mac, I think you get a message prompting you to do a Restore when you connect it to iTunes on a Windows PC (because Windows cannot read or write the Mac disk format). The Restore erases (and reformats) the iPod for Windows. You would not be able to simply access it in Windows (if it is formatted for Mac), even if the version of iTunes is older.

Older iPods can be formatted for Windows and work fine with a Mac, because Mac OS X can read/write the old Windows "FAT32" disk format. But what disk format is used for an iPod classic (especially one with a very large drive), when it is formatted for Windows? I think 240GB is too large to use FAT32 efficiently. And if it uses NTFS, Mac OS X can only read NTFS (not write it). THAT may be why it still appears in iTunes, but it is "disabled" (grey).

If it worked fine before with your Mac, and you did not do a Restore using iTunes on the Windows PC, I can't explain why it is greyed out in iTunes on the Mac now.

OK, so I guess even the BIG-storage iPods get formatted for Windows using good ol' FAT32. FAT32 is somewhat less efficient (especially on larger storage devices), so you may find that you have a bit more storage space if you Restore it using a Mac.

I don't know why it is no longer working for you on a Mac, as is. I have an iPod (much older model) that I upgraded with a 64GB compact flash card (on an adapter). I did the last Restore on it using iTunes for Windows, so it is currently formatted for Windows (using FAT32). It works fine with the latest OS X and iTunes on my Mac; I just tried now to confirm.

My complete library is on the iMac so I'd rather restore it there.

If your complete music library, including the songs currently on iPod, is in your Mac's iTunes library, you can do a Restore on the iPod using your Mac. Doing the Restore using iTunes on a Mac formats the iPod using HFS+ ("OS X Extended" as it's called now). It also erases the iPod, but you can sync everything back from your iTunes library (as long as it has "everything"). After the Restore, just set it to Sync Music with the option to sync Entire music library.

NOTE: The NTFS stuff does not matter. I incorrectly thought that the more recent larger capacity iPods may be formatted using NTFS (not FAT32), when they are restored using iTunes for Windows. That's why I mentioned it, but it not relevant.

Oh, that's right. You mentioned that...

If you can see the iPod in Disk Utility, and use it to Erase the iPod, it will get formatted for Mac. In Disk Utility, you should select the device in the sidebar, not the volume indented below the device. This erases the iPod completely, so it will no longer have its onboard software. But the Restore "restores" the software, so that it can operate as an iPod again. Even if iTunes does not prompt you to do a Restore, you need to do it.

Alternately, you can do a Restore using iTunes on your PC. Then, connect it to your Mac and do another Restore using iTunes on the Mac. Normally, an iPod should be accessible on the Mac in iTunes, even if formatted for Windows. Again, I'm not sure why your iPod is currently "greyed out" in iTunes.

i have the same problem

here is my system log

2015年12月11日 上午1:06:22 kernel[0]: 001398.684072 HS02@14200000: AppleUSB20XHCIPort::resetAndCreateDevice: failed to create device, disabling port

2015年12月11日 上午1:06:30 kernel[0]: USBMSC Identifier (non-unique): FFFFFFFFFFFFFFFF 0x5ac 0x1261 0x1, 2

2015年12月11日 上午1:06:31 kernel[0]: disk1s1: alignment error.

2015年12月11日 上午1:06:31 kernel[0]: disk1s1: alignment error.

2015年12月11日 上午1:06:58 kernel[0]: USBMSC Identifier (non-unique): FFFFFFFFFFFFFFFF 0x5ac 0x1261 0x1, 2

2015年12月11日 上午1:07:01 kernel[0]: 001437.125636 HS02@14200000: AppleUSB20XHCIPort::resetAndCreateDevice: failed to create device, disabling port

2015年12月11日 上午1:07:27 kernel[0]: USBMSC Identifier (non-unique): FFFFFFFFFFFFFFFF 0x5ac 0x1261 0x1, 2

2015年12月11日 上午1:07:28 kernel[0]: disk1s1: alignment error.

2015年12月11日 上午1:07:28 kernel[0]: disk1s1: alignment error.