Tyre pressure warning

[Colincummings]

Hi

Ive had a warning that keeps coming on my 2006 a6. It says low pressure (in yellow) and other times a flat tyre (in red) but the psi displayed is correct and even if I reset the tyres the warning come back on with in 5 minutes but not all of the time. I have double checked the pressure at 3 different petrol stations and I can' see a problem.

Now to top it off im getting a brake pad warning light from the same wheel.

Are the two problems related or not any help would be much appreciated. 

Thanks