Originally Posted by josephhauler
the diff lock light is simply the end (ground) wire from your locker. It most likely has a loose or bad connection to the chassie.
Looking at the wire diagram though, the electrical path for the light goes FUSE BLOCK ---> INST CLUSTER ---> DIFF LOCK LIGHT ---> DLCU.
There has to be a problem with either the DLCU or it HAS a connection to ground when it shouldn't. No wires are chaffed or damaged...
Could be the diff lock position switch going bad as well...