I have an 05 DC 4x4 which has the low tire pressure warning system. First of all, how does this work? My light has been on for several weeks now and I've added/checked all four tires and the light is still on. Then I looked at the manual and it stated that the spare could also be affected. Naturally, when I crawled under the truck, the valve stem wasn't exposed. Needless to say, I haven't checked the pressure in my spare tire. But this light is becoming annoying.