As with all the VAG (Volkswagen Audi Group) car's Audi may have Ignition coil problems, engine will run rough and lack performance, engine management light will be on, without test equipment the only way to find out which coil is at fault is to substitute a new coil, until the faulty unit is found and the engine runs smoothly, if the warning light doesn't go out try turning ignition on and off 6 times. See misfire.
If the DPF light is the only warning light on, you should drive vehicle at over 2000 rpm (to raise exhaust temperature) for 20 minutes without delay, this should regenerate the particulate filter (burn off the accumulated soot) and the light should go out.
If you have DPF light and the engine management light are on together, have vehicle towed to dealer. The dealer will be able to make the vehicle, with the aid of diagnostic equipment go into forced regeneration and clear filter.
Don’t run vehicles with diesel particulate filters on 100% bio-diesel only use EN 590. Only use low ash engine oil (VW 507 00).
Brake light switches can be a problem, it has two switches in one, half puts the stop lights on, the other tells the computer that you are applying the brakes, so it can turn off the fuel injectors, if the engine is coasting, saving fuel and cutting emissions. The engine management light or EPC (Electronic Protection Control) will be on sometimes and the engine will run normal.
Flat batteries can be caused by heated door mirrors and locks staying on or cooling fans not switching off.
If after flat battery, the one touch of the electric window won't work it can be reset by opening, closing, releasing and then hold it on the closed direction for 1 second.
Flat battery on A2 can't open tailgate there is an emergency release, under a cover at the bottom of the rear window, slide cover up and pull on plastic level to open.
Wipers not working make sure bonnet is shut properly or the bonnet switch is working correctly as computer will not let wipers work if it thinks the bonnet is open.
Non start Key warning light on, try leaving ignition turned on, for 15-20 minutes, if light stops flashing the transponder has re synchronized and the car should now start.