I dropped my Caravan off at the shop for a slow leak. When I picked it up they told me it was from a leaking valve stem. Then they said I had to replace the TPMS or the light would stay on the dash. Previously the sensor was not broken and I relied on it to tell me when to fill up the slow leak. I am wondering if the mechanic busted it? Or is it standard to replace both together? Thanks for your help, Christina
While Josh is right they don't usually need to be replaced together, the TPMS is integral with the valve stem. To fix the valve stem may require replacement, which would mean the TPMS would need to be replaced. There are TPMS renewal kits (includes battery, seals, & valve core) which could possibly be used to repair the TPMS, however it may/may not work in your case.
They don't need to be replaced in pairs. As long as the original unit on the other (or all other tires) is good, leave it be.
As far as re-programming the sensor ... if they replace the old sensor, they should be re-programming it as a part of the job. It doesn't make sense to replace the sensor if it doesn't work when it's done.