I'm having a similar issue, 2003 LS 3.9. Started with blacked out EATC but started and ran. Then went to restart then everything electrically in the interior went haywire. Narrowed down to circuit F2.20 fuse blown 10 amp which is EATC, FEM in cab fuse box. Replaced once started again blacked out EATC still. Got it home, went to restart then nothing. Same fuse blown, replaced but keeps blowing as soon as it hits the socket. Checked battery voltage 11.25. Has a dead short somewhere that is draining battery. Once battery voltage drops all FEM and REM goes haywire and systems start to lockout including PATS. Pulled all HVAC relays and DCCV plug to try to narrow down, fuse keeps blowing. Charging battery overnight. Going to try to unplug heated seat plugs and EATC this morning to see if this is where the short is. Could be the heated seat module or FEM. Trying to narrow down the circuits impacted via wiring diagrams I have. All other fuses are fine. Rather odd that the fuse keeps blowing with all other lower amp fuses are good in same circuit run.