have 2011 Jeep Compass, Problem with TPMS

have never had spare out of the trunk

That doesn't matter... If it is low on air pressure... The light will stay on!!... You don't have to use it for it to become under inflated!!! Do you understand?... Why don't you just have the air pressure checked??

will do Thanks, Have had pressure checked , everything perfect. am wary to call jeep because car no longer under warranty & can't afford big bill from them