letsgetrdy

Just to add my two cents, 2016 A4 Avant b9 190 quattro 100k miles C11EC04 with the dash bit saying brakes restricted / start stop gone etc etc. It popped up as soon as I started the car and was after the car hasn't been used much in the last two weeks and perhaps nor for 3 days before that (seems common that if they sit the sensor dies). I drove it 10 mins and then came home as I knew it could brick the ABS eventually. I work on cars alot and even this got past me.. I changed the sensor to a new one from amazon £15, upon plugging it in I had the exact same code. I fiddled with it on and off the car, I then started getting codes for brake boost pressure sensor short to GND and short to POS, sometimes one, sometimes the other, sometimes combined with C11EC04 sometimes not. For reference C054B00 is the code for GND or POS I forget which. So sometimes that code by itself and sometimes that combined with C11EC04. I thought perhaps it was my ABS unit dying as I knew the sensor was good and I also tried an exact same oem audi sensor from my A6 C7 for good measure, same code games. And my amazon sensor worked fine on the a6 c7. Long story short (haha) the sensor was not plugged in correctly. It was not quite seated enough. I removed the rubber seal (car side plug) and seated the sensor properly, this time making sure it latched fully. All cured. To add, it was actually semi latching the first time and visually it looked normal, it pushed most of the way in and it wouldn't pull off from a small tug, making me believe it was properly on. Before you mess around try using a needle and working the small white rubber water seal out, and making sure the car side clip is fully backed off then push the sensor on all the way, latch it properly (it shouldn't be able to be pulled out at all by any tugs) and then plug the sensor back into the car brake booster reservoir. I knew before I started it again that the problem was solved. It just wouldn't yank off this time like I could before, and the short to gnd and pos suddenly all made sense. Goodluck !