That was typically when the self test took place - every key on after a complete power down. It would probably do it after a full write if you waited a couple of minutes. I don't remember what the manual tcase setup looked for so the tcm would know it was in low range. The auto's had a separate switch input plus the motor's positions. It's the one that did the self test after each complete power down which could cause it's own problems on the ones with weak shift motors. It may have even had a naturally closed circuit that it opened. I really don't remember and without looking at schematics and operations I couldn't tell you for sure. I do know it should be fixed with the 2wd OS as the low range shift scheduling becomes null and void at that point.