I have a 2008 Silverado that had a parasitic drain for quite a long time. I started checking amperage draw while pulling fuses to determine the source of the drain. .When I pulled one fuse the amperage draw jumped from 292 mA to 492 mA . Then things got crazy and I disconnected everything. After research and info from Just answers, I replaced the BCM (body Control Module) I also installed a new battery . When I hooked everything up, there is NOTHING. no clicks, no lights, no nothing.. It's as if there is no battery-- Dead silence. I checked the Master fuse on the firewall and it is okay. What would cause something like this .I pulled the fuse box and there is power getting to the box via the cable from the mega fuse on the firewall. Thee is continuity between the slot for the 12V wire and many of the various blades on the back of the fuse box. There just seems to be a major disconnect somewhere. Any help or suggestions would be appreciated.