One problem related to brake light has been reported for the 2003 Dodge Ram 3500. The most recently reported issues are listed below.
Directionals suddenly started blinking fast. Right & left directional don't opperate, right rear taillight doesn't operate, front left headlight does not opporate, both rear brake lights don't opperate, checked all bulbs by certified mechanic. All bulbs are in good condition. Tested all electrical & lighting lines, certified mechanic concluded that the integrated fuse box is defective & needs a brand new replacement. No corrosion present. Ordered fuse block from dealership, parts dept. Confirms these blocks are on national back order, with 1000's of orders placed. Called Chrysler, they said they can't help as there's no vendor making this part yet. If I got a used part for $400, it'd be an old defective fuse box & I'd have exact same safety issues. Apparently many 2003-2005 Dodge ram diesels currently have this same electrical problem.