TPMS battery(s) ?

[arfur]

Occasionally the TPMS alerts me in my BMW of tyre pressure loss.

The car needs 4 new tyres right now, and because of the age of the car I'm thinking that the TPMS might need new batteries.

Looking online I can find stem/valves or the base unit with or without the stem/valve

Which part has the battery in it ?

The difference is 15 quid or 120 quid if its in the stem/valve or in the base unit

cheers

Arf

[Funkstar De Luxe]

The base unit will contain the battery