I recently took my Audi Q5 Sport 2.0 TDI quattro S tronic, UK 17 plate on 50K miles to a new to me independent VAG specialist in the UK for a long-life service inc pollen filter, front pads and discs using PAGID parts and brake fluid. After picking up the car, the brake pad warning light came on, went off and came back on again, so I called the garage and returned the car in the morning. The front pads were replaced by the garage and the rear pads had 30% wear. Despite the owner double checking the work and even trying new OEM brake sensor wires (he ordered in) on front and back pads, he still could find the fault. He also said there’s no way of finding out if the fault is occurring on the front or the rear pads. Finally, he booked the car in at the local Audi dealership in a week to see if they can find out what’s going on. Has this happened to others and what was the fix and how did you get there? I also expect Audi will charge for the diagnosis work – should I expect the independent garage to cover this cost? Finally, what’s a good UK Audi Q5 forum for this sort of question? Thanks!

Sorry to hear of your issue. A similar issue was discussed last year on here:  

If it's not the sensors or the wiring to the sensors then there must be an issue with a brake module I'd suspect. The diagnostic check should flag the issue. 

I think you'll be left to foot the bill as the garage will claim it's not their fault. Unless you can prove damage otherwise. 

thanks - I will spk to the garage.