Mazda reports that some vehicles may experience breakage of the aluminum valve stem on TPMS units when removing aftermarket valve stem caps during routine procedures such as checking tire air pressure.
Some aftermarket valve stem caps are made of brass or have thread inserts that are made of brass. When brass and aluminum are mated together, galvanic corrosion occurs between the aluminum valve stem of the TPMS unit and the brass threads of the valve stem cap. This corrosion can cause them to fuse together, becoming difficult to remove by hand. When force is used to remove the valve stem cap, the aluminum valve stem of the TPMS unit will break, requiring replacement of the TPMS valve/transmitter unit.
Advise customers not to replace their valve stem caps with caps that feature brass threads. In the event of requiring a cap replacement, advise them to use only an aluminum or plastic valve stem cap. Also, make sure that the replacement cap does not feature internal brass threads.