Code Breaking allows a character to bypass security systems such as passwords and computers and, more commonly, locked doors and containers. This skill uses up, and is best used with, any Mental Points available, but even if one has exhausted one's mental state, Code Breaking will still work with diminished effect.
In GearHead 1, unlocking doors is a very easy way to gain 50 XP; in GearHead 2 far fewer points are awarded for a successful security breach.
Code Breaking is required to complete some side quests, like retrieving the Argoseyer biomecha.