So: DiskWarrior (DW) won’t rebuild your disks because of your 2153,4903 errors. What that means is that DW can’t unmount your drive.

Here’s what to do:

(But first: you’re on your own!  If you follow the advice below, and totally trash your drive, I’m truly sorry, but I’m not responsible, since I’m just telling you what worked for me. YMMV.)

First, reboot and try again, without anything but DW running.

No go?  Darned sure that nothing IS using the drive?  Willing to take a chance?  OK, then – do this:

1) Run Disk -Utililty- (from Apple). That will get you a list of all your drives, including the one that won’t unmount. Leave Disk Utility running.

2) Go to the finder, and control-click on the drive, and select “eject.”  It will complain, and offer you the option of using “force eject” instead. Choose to force-eject the drive. (This may take a couple of clicks on the “force eject” button.)

3) Once the drive has ejected, return to Disk Utility and highlight the -volume- that you just ejected. (Yes, it will still be listed.)

4) choose “Repair Disk” under the first aid tab.

5) let it do its thing.

6) NOW, go back to DW and select that volume again from the popup menu. This time (at least for me) it will work properly.

7) Reboot.