Having an issue with my 2003 suburban LT 4WD. The light on the module for Auto/2wd/4hi/4lo will all work and go into the right gearing correctly. However the "Service 4WD" light comes on after a few hundred feet of driving when either in 4hi or 4lo. The green 4wd symbol light also does not come on no matter what I do. It seems like the 4hi/4lo gears are functioning correctly and I can feel it working when I drive. I've unhooked the battery overnight and checked the trek fuse as well with no solution. Any ideas what I else i can try? I feel like this is an electrical or module issue but im not sure. Thank you