Re: 4X4 low!!!
Another thing to try before spending the money on sensors: Park the vehicle on a downgrade when you put the transmission in neutral, more the Xfer case to 4LO and let it roll slightly to engage (hopefully it does). Keep in mind that if it does engage, you'll have to repeat the procedure to get it to disengage from 4LO.
If you haven't replaced the Xfer case fluid in the last three years or 30K it'd be wise to do so, along with a visual inspection if the case allows.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!