Why won't the 4-wheel drive engage on a 2002 Ford Ranger XLT when the fuses are good and there are no strange noises?

If absolutely nothing happens when you turn the switch then it is almost definitely the four wheel drive module. It is located behind the right side (passenger side) kick panel. It is a black box and is usually clearly marked. It has one or two electrical connections (plugs) and is incredibly simple to replace. A new one runs between $100 and $120 Point of advice, I have been wondering where this part is, because I have the Haynes manual for my '01 Mazda B4000, and it told me it was on the DRIVERS side. Looked, nothing there. So just be wary of what Haynes and Chiltons says. They are most certainly not always correct. Also it could be a vacuum leak leading down to your module,check on passanger side of the inside fire wall you should see two plugs with vacuum lines,unplug the lines and run a vacuum test on them,your module should hold steady of 8psi if it bleeds off then its your module,and it needs replaced