Hi, My Graphic Display Module only lights up the front two wheels instead of the rear two or all four like it is supposed to... even in low range, the "lo" and the two front wheels light up, but not the rear two...

I have a 97 GC with the 249 (quadra-trac) T-case and the 4.0L engine...

Any ideas to what would cause this to happen?
Is there a separate bulb in the module for the rear wheels?
Could it be a bad module?
A bad sensor/switch on the T-case?

Any insight to how exactly this module works would be greatly appreciated, or any previous experience with this or related issues...

Cheers
Dave