Current draw killing battery(s)

[Keith Seymore]

Howdy everybody.

Vehicle is a 2004 2500HD Duramax.

I have a slow draw which can kill my batteries overnight.

I unhooked the power and jumped one battery with a test light (ie, from battery positive post to test light, then test light to positive cable. One battery only; other battery positive cable disconnected).

I pulled every fuse and relay one at a time in the underhood BEC, the LH end of the instrument panel and inside down by the driver's left foot (boy - are there a lot of them).

None of them killed the draw.

Is there another fuse block I'm not thinking of? Is there something drawing power that is not fused?

It has an aftermarket remote start that I do not use; I have an aftermarket electric fuel pump, which is one of the fused connections that I pulled. Also aftermarket trailer brake controller. Everything else is OE.

Thanks in advance -

K