Q4P3 was a protocol droid who was once sent to Mustafar to retrieve the "Codex" for his master, Pann. While there, he spoke with several of the droids hoping to discern the location of the "Codex". One of the droids he spoke to led him to believe that he had found the "Codex", but he was not able to get to it due to the fierce animals on the planet. Instead, he waited inside the Mensix Mining Facility for someone he could hire to retrieve it.
Soon somebody came along, and Q4P3 gave them a scanner to read the droids who he thought had found the "Codex"'s memory, as it had broken down outside of the facility. The individual soon came back with the item, which turned out to in fact be a Sith holocron. This was not what Q4P3 was looking for, but he paid the individual for performing his job anyway, and let him keep the holocron.
Q4P3 appeared as a non-player character in the video game Star Wars Galaxies, a massively multiplayer online role-playing game developed by Sony and published by LucasArts, prior to its closure on December 15, 2011.