@ibesiano
Hi,
Nobody has replied so simple input from me.
Brake Pad Wear Dash Warning.
An erroneous brake pad sensor warning on the dash is a common fault. The root cause is a discontinuity in the two wire circuit to the brake pads that is part of the four wire loom to the passenger front wheel. This often cause by rough handling when the brake pads are renewed, connectors not engaged properly if at all or cut off! or incorrect pads with no wires or other reason such as corrosion or a breakage in the wires higher in the wheel arch due to flexing. Not sure what you mean by front and back sensor there is no brake pad sensor. (There is the ABS sensor on the wheel hub that measures wheel rotation but this is quite separate.) The two wires in the loom form a continuous loop (earth I assume), the end of which is embedded in one of the pads well below the surface at the wear limit. Eventually the pad wears down to this level and subsequent wear destroys the wire, the lack of circuit continuity is picked up and the warning appears on the dash.
As to remedy. You say you have inspected for obvious damage to the loom so I suggest next you release the connector below the Y fork and clean with contact cleaner and reconnect firmly. If the dash warnining still persists, it maybe a dodgy connector, there is a thread, one of many on this overall problem if you search for repairing it. Others have spliced in a two wire loom to replace existing. It might be an other discontinuity but to be honest many members at this point simply cut the wires and twist together to reinstate the circuit and monitor pads manually. I cut into the loom in the engine compartment and was shocked at the amount of corrosion on the two wires and I still have a dash warning when twisted together here!
AUDI recognised there is weakness here and issued a repair loom for a proper repair, part number 8Z0 927 904 costing about £60 if you prefer this route. It is basically the entire four wire loom and connectors from the front passenger wheel hub to the passenger front footwell, but members often splice it to existing in the engine compartment to avoid the hassle of getting it though the dash.
AIr Bag Dash Warning.
My impression is a genuine fault with this is quite rare, but a common occurrence is when a front seat(s) are removed and for some reason/accidently the ignition is turned on. The startup diagnostics pick up the missing airbag(s) and illuminate the dash air bag warning light. Unfortunately it will not be cancelled when the seat(s) and air bag connector(s) are reinstated and the only way to clear it is with VCDS. My guess this had happened under previous ownership and something I would check out first.
Hope this helps.
Andy