98 Blazer 4 wheel won't go in

98 Blazer with three buttons on the dash for 2 wheel , 4 wheel hi ,and 4 wheel lo. The two wheel button is lit. I push either of the 4 wheel buttons and they blink 2 or 3 times and nothing happens. The 4 wheel hi or lo light will go out. The 2 wheel light stays lit the whole time. Last year the system worked fine I did not try or use it since last winter. Any hint on where to start looking will be appreciated

Ground pin 13 on diagnostic connector and check shift buttons for codes.
post back any codes.

Look wiring and plugins over good.

Does the shift buttons all come on for a bulb check key on?