Our warning sound and alerts come on the dashboard every week regarding low pressure on tyres. So, obviously we've checked and pumped up tyres, we had new tyres fitted because two were worn, nothing to do with warning lights, we mentioned it to the garage they said they've changed the valve. Anyhoo, lights continue to come on, we had the car serviced at a specialist garage mentioned it again - they stated the same, the valves, they changed them. Took the car to actual BMW garage mentioned it again as still stating warnings ⚠️ they said it'll be the sensors - they said all fixed - guess what.... no it isn't! We've had the car for 3 years and no one can seem to detect anything!! Frustrating! 

Morning Sam

Welcome to the Forum

I have had similar with the 3 X5's I have owned, 2 x E53 and the current E70 

The first a 2002 E53 sadly got squashed by a falling tree before any fix, it's replacement E53 2003 went through a similar process to you in the end I turned off the warnings. 

But I can't stand having things that should work but don't, so I began my own investigation (I have a full diagnostic suite on a laptop) It was while checking something else that I found a poor earth connection in the boot (BMW use common earth points plus earth switching) I cleaned and remounted the earth comb and a couple of systems suddenly came back to life. I checked the TPMS and guess what that worked as well I think a lot of Garages are lazy and just assume it's a sensor issue. I still have the E53 but the Daily driver is now a 2009 E70 TPMS started playing up I found 2 faulty sensors (but cleaned the earth points as a check) I brought new sensors from Amazon less than half OEM cost and they worked straight out of the box biggest faff is tyres off to change them (wait for tyre change if possible) The E53 now has the same sensors, all work and no issues for 3 years now (stupid boy tempting fate)

Dave