Re: 2000 navigator 4x4 light keeps flashing
If it's electronic 4wd (ie, knob on the dash), chances are good the TCCM, or transfer case control module is toast. If so, it's best to get a used one and save yourself hundreds over a new unit that can quit even before a used one.
As mentioned, best to get the code(s) pulled first to narrow down the problem.
If it's been 30K since the transfer case was serviced, it'd be a good idea to take it in for a fluid change. Transfer cases are often overlooked as they only hold a quart or so of fluid (sometimes two quarts in larger units), and the fluid is hard to keep cool unless the vehicle is constantly driven on the highway. Fluid breaks down from heat, and so on....
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!