consultation

Hello, I would like to ask you, I have a problem with a Ford F 100 4x4 2007 because of the drop it works but the low I make the change of the selector when I put 4x4 light the light passing to the other point I do not change I would like to know if there is any electric plane to find the fault if there was an electric plane there would be like it, it would be like if they could pass it to me.