According to the wiki:
QuoteIn Mr. Scott's Guide to the Enterprise, it was stated that if the code "0-0-0-Destruct-1" was given, it would result in an overload of the warp core (most likely an intentional warp core breach, although that term was not used until Star Trek: The Next Generation). This version of the auto-destruct was meant for use in deep space, nowhere near a planetary environment. Using the code "0-0-0-Destruct-0" (as it was in TOS and Star Trek III), would render the ship as a useless hulk to all hostile forces.
"0-0-0-Destruct-1" is presumably the method that they were planning to use in TMP, which Scotty said would take V'ger with them. That would have been a good way for Kirk to go out, flying the Enterprise-A into some galactic-level threat and detonating the ship's antimatter.
