I had the same problem. My 93 would go into low range most of the time but not into high range 4x4. When it would attempt to go into 4 high, both low and high range lights would flash and then it would stop... My mechanic had to replace the electronic shift module on the transfer case, the vacuum acctuator on the front differential, the safety neutral switch, and adjust the shift lever. After all that it works fine. Cost me about $489...