 They can be mounted on the back of the tire's valve stem or attached using adhesive or to a band which is then securely wrapped around the rim inside the tire, usually in the drop zone.When the direct TPMS warning light comes on, either one of the tires is under-inflated, severely over-inflated, or there is a fault with the system.If the light is constant then inflating to the correct placard pressure should turn it off.