Don't buy the original sensor from Tradition or Audi UK for £369 (4D0927803E)
Step 2:
Buy Audi A4 8E rear abs sensor (8E0927807B) for around £38
Step 3:
Remove the old faulty sensor from the car and remove the 2 abs sensor pins from the 4 pin connector using a de-pining tool. If you want to be a cowboy you can just cut it off, and solder new sensor cables to the old sensor pins still in connector housing (the other 2 pins are for brake pad wear sensor):
Step 4:
Line up the old A8 sensor with the new A4 sensor, and move the cable grommets on the A4 cable so that they match the A8.
To do this I pushed a small screw driver through the grommet, and sprayed silicone grease inside the void it created, you need to be quick as the grommet will become movable for about 30s before it once again sets and sticks to the sensor cable:
Now you just have to feed the new sensor through the joint connector housing grommet, heat shrink it like the original sensor was (take pics as you go along) crimp on new terminals (000979132E), and insert the crimped terminals back into the connector.
Fit it all back together and job done.
I reckon A4 abs sensor + all the tools and supplies needed will cost you ~50 pounds instead of £369 (UK Price) which is a huge cost saving.
You will end up with the exact same part, and same quality as long as you are careful and take your time.
First time round it took me 3h for this all in, as the bolt which holds the sensor snapped, and the sensor was stuck in the upright so i had to drill & chisel it out.
The sensor wiring took me 45 mins the first time, and 20 mins when I did the other side.
Your ABS sensor light/code should automatically disappear with the new sensor correctly installed.