4x4 stuck in 4 wheel high on 2002 Chevrolet Silverado 1500

indicator light says 2 wheel high, but is locked in 4 high... and now when shift truck into reverse it changes the transfer case into neutral... so it wont back up...put back into drive and it goes to 2 wheel high, but it is locked in 4 high.. the light just says 2 high..

Asked by for the 2002 Chevrolet Silverado 1500
scan codes and post so we can adv