Swapping out the fuel tank flap motor / solenoid
One of the known faults with the B8 is the fuel tank flap motor which can go bad, causing the flap not to open when the central locking is actuated. Since this is a common problem with the earlier 09-10 B8, Audi have released several updated versions of the motor.
8K0 862 153 H - Newest version of the motor
T25 torx driver
small flat-head screw driver
microfibre cloth or an old t-shirt / rag to protect the paint
This is a simple job and mostly anyone can do it.
Open the flap if you motor still has some life left in it and the problem is only intermittent. If the motor is completely dead, open the flap via. the emergency release handle, which can be found behind the right side compartment in the trunk. Pull on the red handle to release the lock and open the flap.
Unscrew the single T25 torx screw holding the plastic trim to the motor. The next thing you need to do is locate the 4 recesses on the plastic trim, marked in red in the picture, puncture them and insert a small flat-head through the opening and release the clips. I found it easiest to release one clip at a time while pulling on the plastic trim. Once all clips are loose, the trim can be slid toward the back of the car and left hanging from the fuel cap. Protect the side of the care with something unless you're also removing the fuel cap. If you remove the fuel cap, stuff a clean cloth in the opening to prevent any dirt from getting in to the tank.
Find the wire going to the motor in the same trunk compartment as the emergency release, and pop the plastic holder off the convenience module surround to free the wire, marked in red in the picture. Go back to the tank motor and slide the motor toward the front of the car to release it. Unplug the connector and pull out the emergency handle and cord.
Installin the new lock is just the reverse of removing the old one. Simply run the emergency release to the trunk, pop in the electrical connector and slide the new motor in place. Pop the plastic cover back on and screw in the T25 torx screw. Make sure you don't forget to clip the emergency release handle and the wire back on to the convenience module surround to prevent rattles inside the car!
The plastic trim will have 4 holes now, and you could replace it if you wish as it's quite cheap, but the only problem is that it comes with the tank flap, which will need to be repainted so I suggest you either spend the extra cash and have it painted or live with the 4 holes. I decided not to replace mine as the holes don't bother me.