a friend of mine has an 04.5 lly and is having problems with the ecm we're scratching our heads as to what it could be. the truck will not start and there is no power at the ecm fuse in the fuse block what would cause no power at the ecm?
Have you pulled the fuse out and checked to see if there is voltage on one terminal? Seen people jammed wires into the fuse panel for aftermarket stuff but is then removed. After that the fuse doesn't make a good connection.