The Parktronic Parking Aid Module is located in the trunk behind the left (driver's) side panel above the Satellite Navigation CD unit (along side the rear fuse box). Removing the left side trunk panel exposes a steel framework that holds the navigation unit on the bottom, the parking aid module above that, and a third battery / electronic functions module on the top. Removing a single bolt will allow the section that holds all 3 modules to be swung out and detached from the base of the framework so that any of the three modules can be removed and serviced. Below is a picture with the left side trunk panel removed showing the location of the Navigation, Parking Aid Module (see red arrow) and B-E-F module on top. This same location was also used for the new module when my car was up-graded in 2015 to a more modern Parking Aid system (necessary for direct interface with the modernized in-dash head unit).