Replacing a faulty rear PDC Sensor

[IT]

A PDC sensor failure is inevitable. There are 8 of them on the FL D2, and they will fail over time. Its dam annoying. If one sensor fails, the whole system goes off, with the PDC button light just flashing at you rather unhelpfully everytime you select reverse

You can buy a brand new one from Audi, and paint it, or speak to the nice people at a8parts who will not only have one much cheaper, but if you're lucky, they might have one in your colour. Whilst silver isnt my favourite colour, it does make jobs like this easy as they could supply a silver one off the shelf

So first, we need a bit of VCDS (aka vagcom) action to determine which is faulty. So, first clear all the fault codes. Then activate the PDC and walk round the car, using every sensor, rubbing your fingers over them a little agitate it - Then, recheck for errors and the one(s) that are faulty will reveal themselves.

In my case, its the mid rear right. These are always given as if sat in the drivers seat. So, rear middle on the right is the second one in from the right hand side on the back bumper:




Also note that if you're struggling to suss exactly whats going on, use the measuring blocks feature and you can read the distances that each PDC sensor thinks it is away from an object. So, you can walk round the car and check the accuracy of each sensor to see if one isnt really playing ball



Tools. Most importantly, something soft that the bumper can come down onto so it wont scratch. Also need a cross head screwdriver, a flatblade is useful, and a 10mm Allen key.




So, we go under the rear of the car, and we need to drop down the plastic cover. Its held up by 4 crosshead screws. No need to remove it, just drop it down so it gives us the access we need:



And here it is dropped down:



Once the cover is dropped down, we can access the 2 x 10mm allen bolts. They are easily seen when looking up at the bumper from underneath.




Remove the bolts completely:



Next, we need to sort out the rear wheel arch liner as it will foul up the bumper coming off:



Its not held in by anything, and will just prize out. Its easier if you pull the bumper back slightly:




Pull the bumper out a bit further, and then you can disconnect the cable for the PDC sensors. I didnt have to on this car as the clip holding the connector popped out giving me the play I need.




Either way, then pull the pumper out completely, and lower gently onto your protective surface:



You can now see the PDC loom running along the top of the bumper beam:



You can either pop the two plastic clips to one side to release the sensor, or remove the torx to release the whole sensor and bracket. I popped clips as it was quicker:



and out she comes:



Disconnect the sensor:



Here is the replacement sensor I got from A8parts. It was in its holder, so I removed it from that to pop straight back in:



Plugged back in:



and pushed into place:



now - Bumper offered back up into place where it will sit happily:



Nows a good time to test again before we bolt everything back together. So, reset all codes. Perform a full walkaround test and see if anything fails.....

And if alls well, you'll end up with something like this:



In which case, you can refit in the reverse order:

• Wheel arch liners back in place
• 2 x 10mm allen bolts back in
• Plastic cover back in place with 4 crosshead screws
• In my case, wash it (!)

[Johnmed]

Great stuff. Very helpful.