You told Jack there's no list on the website. Where do you think I got my info from?
Western Digital Diagnostic Error Codes List!
Secondly, why exactly are you using the WD Diagnostics on it? Is there a problem you're having?
Are you trying to use the diagnostics through Windows? I wouldn't be surprised to see a "locked" error if you're using XP, as XP often will not allow actual hardware level device access as a security measure.
Always provide more information. Is the drive acting up in some way?
Have you tried other companies' Hard Drive diagnostics?
Can you access your files? Is the drive new?
Have you done an antivirus check? Don't just rely on whatever AV you have; try different ones. Go to the free Housecall virus scan site that does it right over the web via your browser:
http://housecall.trendmicro.com/
What model drive is it? Not just size, the actual model number.
There's a lot you need to fill us in on. Please elaborate on the above.
And again, what is prompting you to even check the drive's status via diagnostics?
If you know how to burn an "ISO" Cd, you should get the "Ultimate Boot CD". It's absolutely free, and has tons of utilities on it in an easy menu. Once you burn the iso file (burn it using the ISO format in your burning software), you can put the CD in your drive and boot up your pc with it. This assumes you have your boot order in the bios set to boot from CD first.
You'll see the menu right away. There's a Hard Disk Tools menu option. Go there, and you'll see about 5 or 6 different hard disk diagnostics programs.
http://www.ultimatebootcd.com/download.html
Steve Gibson has an excellent Hard Disk Diagnostic and repair tool called Spinrite 6.
It's not cheap, about 89 bucks or so, but an awesome tool to have.
http://www.grc.com/sr/spinrite.htm
Probably the best drive utility out there. There's a 6 minute video you can watch that explains how it works.