l wanna replace the stock 16'' rims with 18'' rims from a Mazda CX9.l do not know if l have TPMS in my stock tires.If l do, can any chain place (Firestone, Tire Kingdom, etc) replace the valves and TPMS without a problem?
They screw out and screw back in?What screws out/in?The valve and it has a built in chip in it?Or something else?If it is something else, will it fit in a different brand of wheels?
Thanks for the great answer, Gearbox.

However, are you sure that l do not have it just because l do not have a dash light?l do have a computer in the dash that gives warnings when necessary

TPMS is mentioned in my handbook (but is generic for all '06 Mariners).l have the Luxury model with the computer.
l just answered my own question:
http://nhtsa.dot.gov/ncap/cars/3542.html

''Tire Pressure Monitor: Std''

yes they just screw out and replace in new rims ,we had to do that at ford when we got some bad rims we just took them out and put them in new rims. hope this helps,

While it is not recommended to change sizes & such, yours does not have TPMS at all on it.. there would be some sort of light on the dash for this & yours does not have it.

Meaning, u can put the rims on if they fit the bolt pattern

Also JT ... There r many styles of TPMS Ford uses now

The vans use rolling speed to determine fault
The expeditions used the sensor mounted in the stem (which proved to be a headache with so many people breaking them)

Almost all 07 & newer with TPMS use a sensor mounted internally to the rim with a band. the band has to be replaced with a new band (the sensor can be moved), but Ford builds bands for up to 24 inch tires (but does not recommend TPMS for over 20s due to false alarms)