After some Googling, I've found this excellent and simple method by Ivan Glisin which works very well:

No need for 1.30. Do the following with 1.31:

In the root directory of your memory card create or copy a text file named

MODSET.TXT

with only one line in it:

[OPEN_DEBUG_MENU]

After inserting card back to the camera, to enable debug mode do the following:

1. Switch camera off.
2. Open card door and leave it open.
3. Switch camera on -- debug menu shows up.
4. Close card door.
5. Left/right to enable debug mode.
6. Press OK to confirm.
7. Go to Set-Up menu, go to the end and Set-up will change to TEST MODE menu, AF TEST option is there with Focus Corr inside.

To disable debug mode:

1. Switch camera off.
2. Open card door and leave it open.
3. Switch camera on -- debug menu shows up.
4. Close card door.
5. Left/right to disable debug mode.
6. Press OK.

Note: you can permanently leave MODSET.TXT file on your card.

Read more at: http://www.pentaxforums.com/forums/pentax-dslr-discussion/128474-need-k10d-firmw...#ixzz1DHfb0nZE