This truck runs like a top all summer and fall, in the winter no start, tow over, when we take it to the mechanic in a warm garage starts right up, drive it home, next day forget it. Have tested everything electronic nothing shows up on the diagnostic, have replaced everything known to man, ignition switch, plugs, complete overhaul kept up well and still nothing. Our other vehicle starts right up in the same cold temps...any suggestions? Showing Wife's e-mail below. New Battery. This vehicle is not a Chevy El Dorado don't know why it says it on my vehicle description...is a 2003 GMC Sierra.