I had the same problem as others (‘brake servo restricted’ warning followed by a ‘stop/start not working’ message) with my 66 Reg A4 Avant TFSI which had only done 24,000 miles and was used only very occasionally during lockdown. Because the brakes still worked and the display message said I could continue driving I did so but only for a few very short journeys (and after the first time the ‘thud’ of the ABS kicked in I then made sure I applied the brakes even more gently) and intended to get it booked into an independent Audi garage (cheaper than main dealer) when convenient. However, after reading in the forum about the ABS issue (which clearly added urgency) and Simon Ryder’s report on how to change the pressure sensor I decided to give it a go without any further delay. My A4’s pressure sensor 5Q0906207(A) can be bought online for about £50 but as my Audi wasn’t on the website’s list of models that the part fitted(!) I decided not to take a chance and instead bought it direct from a main Audi dealer for £75 incl. VAT (as this meant a 40 mile round trip I paid £4.99 + VAT for it to be posted to me although the postage only cost the dealer 65p). I’m no mechanic but it was really easy to change, took less than 5 minutes, and everything is back to normal. I’m just so relieved that I was able to sort it for £75 plus postage AND before the ABS became an issue, so two fingers to Audi and a big THANK YOU to Simon.
