A small electric motor built into the rear brake calipers applies the parking brake. This is a known weak point of the B8 platform (A4 B8, A5 8T, Q5 8R, allroad B8): moisture and road salt get into the motor housing, the electronics corrode, and the gears seize. The symptom is a parking brake that will not apply or will not release, with a fault message.

The membrane of the crankcase breather regulates how much suction there is inside the engine. If the membrane tears, an unregulated connection opens between the crankcase and the intake, and oil vapour starts towards the intake from there. This gives oil consumption, a whistling noise under load, and mixture fault codes from unmetered air. The oil reaching the intake speeds up the carbon build-up on the intake valves, which is already heavy on this engine, because the first and second generation are pure direct injection, so no fuel washes the intake port. The tear is reported between 60,000 and 80,000 km, and the repair is replacing the breather module or the cam cover with an adaptation afterwards, between 80 and 400 euro. On the first generation (CGWB and CAKA, between 2008 and 2011) the breather works with low suction, so a noticeable suction at the oil filler with the engine running is normal. From the second generation the system deliberately gives more suction, with a different part. The oil cap test on its own therefore does not decide whether the breather is faulty, and this is where unnecessary part replacement usually comes from. In March 2013 Audi issued a service bulletin on the oil consumption of the supercharged 3.0 TFSI (17-13-37) and named the 2009 to 2012 A6 and A7, the 2011 to 2012 Q7, and the 2010 to 2012 A4 and S4.

The front suspension of the longitudinal engine Audis (and the Seat Exeo derived from them) works with four control arms per side: two above, two below. That gives excellent steering when new, but it also means four ball joints and eight bushes per side: sixteen wear points at the front in total.

Channels around the sunroof frame carry the water away, leaves, dust and dirt block them, the rubber valve at the end of the channel sticks shut, and the water runs into the headlining, the A-pillar, the footwell and the boot. On the B8 A4 this often leads to electrical faults: you often miss the water and notice instead that something electrical starts behaving oddly, and by then the control unit in the floor is already corroding. Cleaning the drains is a cheap repair, replacing a soaked control unit is expensive.

With direct injection the fuel does not wash the intake valves: the petrol goes into the cylinder, not behind the valve. The oil mist and soot arriving through the EGR and the crankcase ventilation therefore build up on the valve stem and head, and from 80,000 to 100,000 km they restrict the flow. Symptoms are hesitation, loss of power, a rough cold start and misfire. It is not a part failure: it is a consequence of the design, and therefore it comes back. Cleaning (walnut or dry ice blasting) helps for a few tens of thousands of kilometres.

The G62 sensor tells the engine control unit how hot the coolant is. If it is faulty, the control unit thinks a warm engine is cold, and runs it rich: hard warm or cold starting, a rough idle, markedly increased fuel consumption, and a dash temperature gauge that jumps around or never reaches its usual reading. The part is cheap and can be replaced in half an hour: the trouble is that many people do not recognise it and replace an injector or a lambda sensor instead. If the fault persists, the rich mixture can destroy the catalytic converter too.