[ainarssems]

It's inside ABS unit.

I had one of those codes for A6, don't remember which. In my case it was sticking master cylinder not fully releasing. Sometimes if would stick for a bit and release but on 2 occasions it was not releasing, brakes were dragging a bit so calipers heated up as fluid was heating up and pressure building it was braking more and creating more heat and so on until could not even move in 1st gear. 1st time it released after cooling down for 45 min, second time I had flare nut wrench and brake fluid with me just in case so released pressure undoing pipes by ABS unit, topped up brake fluid and was on my way. It was about 2 or 3 months between occasions. I had already bough new master cylinder in that time but had not changed it yet. I changed it next day after it happened second time. Has been fine since.