I have a 01 Ram 1500 4x4 and all of the sudden (after 3 days of ice and snow) the 4wd light started flashing and when I would let off the gas it would come back on. Vacuum leak right? Well I checked all the connections and found no leaks so I bypassed everything by running a new vac hose direct from the intake to the cad. All four tires spin but the 4wd light is off. I pulled the switch out and pushed the plunger with my thumb and on came the light. Any ideas on why the light won't come on normally?