[cr0sh]

As a counter to that point - unless you're willing to spend mega-$$$ on a high-end scan tool, you won't be able to read all of the OBD-2 codes.

Even with such a scan tool - there may still be certain codes that are "manufacturer only" readable.

[thefiregecko]

The more I learn about this the more disappointed I am. In my own experience the standard codes have always been enough to show me what needed fixing. I'm not a mechanic though so my range of experience with it isn't that large.