Overnight battery drain on 2001 vs LS

[Clava]

We recently purchased a 2001 V6 LS for my 16 yr old son. His first car.
The battery is a 5 yr old Duralast. Overnight battery goes dead. It has a 3.3 amp phantom drain.
When fuse number 20 in the central junction box is pulled the drain stops. This controls so much. Dash lights ,etc. Neither will the car start.
The car doesnt't have any aftermarket stereo equipment yet. Factory radio only.
Battery drain seems way too common on these cars.
Any ideas anyone?
Thanks.

 

[joegr]

Actually, considering the complexity of the LS, I don't think they do too badly in terms of problem drains. The real issue is that when they happen, they are very hard to correctly diagnose. This is a problem for all cars these days.

Anyway, I can look up what all is off of fuse #20 and maybe help some. Which fuse box do you consider to be the "central" one? (trunk, dash, or hood?)

 

[Clava]

I have the car at a shop and I believe he said it came from behind the passenger kick panel. It is too late tonight to call him. Will talk with him tomorrow.
Thanks for any help you can offer.