TPMS Fault

[Ron F]

TPMS fault warning coming on regularly and 2 visits to Audi dealership and they can’t find any fault. Tyre pressures etc have been checked multiple times and reset but no luck. Any thoughts as to the cause 

[Magnet]

Welcome Ron and thanks for joining.

’Tyre pressures have been checked multiple times and reset…. ‘ 

So are you saying that the tyre pressures need resetting -in response to the TPMS warning - so they are actually lower? than the required pressure? 
Regards,

Gareth. 

[Ron F]

No, the tyre pressures are always okay when checked. It’s not saying that a specific tyre is low on pressure as it would if there was a puncture etc but that there is a fault with the system. I have found out that it is not sensors in the valves that monitor the tyres but a combination of the rolling circumference when set which is monitored by the speed sensors/ ABS system