06 Civic (FD) has 1659 CEL and Parastic drain

Hey guys, I have been watching Matt’s videos for a while but this is my first time posting on the forum.
I am actually trying to help out someone, I am a distance away from them so I’m getting this info as per his statements.

Said person was duped into buying an 06 Civic (FD) with a myriad of issues. While he managed to tackle the mechanical issues, the electrical problems are proving to be a pain and challenge.

As of right now, he has a CEL (P1659) related to the throttle body, headlights do not work, or if they do its intermittent, he has a parasitic drain that caused him to change 3 batteries and 2 alternators (ouch). He had an issue with the cooling fans but managed to sort that out.

He said he was able to trace the parasitic drain to a wire that is bundled with 7 other wires, the socket of which is feeding from the external fuse box (engine bay). He believes that the parasitic drain and throttle body issues are related, he added that if he disconnects the socket with the 7 bundled wires, the parasitic drain stops. He replaced the fuse box with a new one and the parasitic drain disappeared along with the check engine light.

Then he attempted to try the headlights (albeit the battery was severely discharged when he did) and that’s when he heard clicking emanating from the dashboard for some time before everything died. So, he got a new battery and after connecting it was surprised to find that the CEL has returned along with the parasitic drain. He said he read online that the parasitic drain is a common issue on 06 civics and that it is caused by the internal fuse box (below dash). He says all wiring and grounds are ok (I highly doubt that, given the nature of his problem).

He needs help with the problem, and is also looking for wiring diagrams for:
1. Fuse box wiring to throttle body and ECU
2. Fuse box to headlights
Any help would be appreciated, thanks.

TL;DR 06 civic has CEL code 1659 and parasitic drain, intermittently working headlights, owner believes drain is caused by throttle body wiring. Help.