Hello
It seems as if I have the same type of problem. I have a 1999 ford f250. It also has the shift on the fly switch. I have measured the resistance of the switch in both 4 hi and 4 lo positions. The switch looks like it has a resistor between each contact so the readings are not a direct short. The voltage measures 6.2 volts ( which seemed odd to me). According to the prints I have it looks as if the selector switch transfers and input back to the GEM module and then the Gem module turns on the correct relays to engage the motor on the transfer case. Is the correct ? I do not exactly know where the GEM module is located but I believe it is next to my emergency brake peddle. Is that correct? I t looks as if my problem might be the GEM module, because the switch seems to be working, but I don’t know for sure. Could anyone clear me up. I might be totally wrong.