How and where did you det to use VAG-com ????
(Diagram now attached)
if all your ultrasonic sensors are ticking will indicate they are ok most of the time if like me it wont help unfortunately 1 faulty sensor front or back will fail the entire system. then the problem is which one. to change .
to locate my faulty sensor I used VAG-com v704.1 which can be downloaded free off the internet onto a laptop Now for the bad news you will also need a lead to connect the laptop to the cars diagnostic socket bottom of the dash above the accelerator pedal
The lead I used which appears to work on all modules in my cars electronics is made by www.SKPANG.co.uk is the KEY-USB+ duak K Dongle.
G7enn If you have not got VAG-com may be somebody else on this forum who live local can help.
Below if a brief description of how to check your sensors with VAG.com
boot up the laptop and start VAG.com Plug your lead into the laptops usb and the cars Diagnostic socket
turn the cars ignition key until the warning lights display ....... this method has to be used for all modules vag.com will tell you to switch the ignition off when checking the airbags
press Options select usb if you dongle is usb and press test .... if all is ok vag.com will say the connection to the car is ok. ... if not try unplugging the usb connection and plugging back in and testing again..
if the test is ok and you have a connection go to the main page of Vag.com . (if the connection has failed you wont be allowed access)
on the main page on vag.com click the following buttons.....select control module......electronics1.......76-park assist
on entering park assist click on measuring blocks in basic functions
you will see 3 groups off measuring blocks one above the other not showing much of interest at the moment all 3 displaying group 000
click on the + buttons on the first block to 001 this is displaying the distances in mm of all four front ultrasonic sensors volunteer somebody to walk up to a front sensor one of the values seen will change check all 4.
click on the + buttons on the second block to 002 this is displaying the distances in mm of all four rear ultrasonic sensors volunteer somebody to walk up to a rear sensor one of the values seen will change check all 4.
any sensor that fails to change in value or is vastly different from the other 7 will be the faulty unit.
hope this helps