It appears that I have a wiring issue with my 2007 A8L. The error code pulled stated that the Rear Left center sensor is bad.
I walked around the car and heard all the sensors clicking except for the one posted in the error code.
I swapped in a new sensor and still no good. I took the suspected "bad" sensor and moved it over to a known good one and it started clicking right away.
Yuck. Sounds like a wiring issue now.
Does anyone know or have a diagram of where the rear parking sensors plug in to?
I traced as far as I could (really only a few feet). It starts going up in to the bumper.
I only removed the 4 screws in the back bumper to gain access and never removed the entire bumper.

Thank you anyone for your suggestions.