Repeating from the manual. The instruction can be found in the Concert Sound System Operating manual, Page 40. It’s for Concert II audio. Hope you got the same one.
Just one question: How do you know Concert Audio is manufactured by Blaupunkt?
Press “SCAN” and the RDS buttons (1 & 6) at the same time and hold until 1000 appears in the display
Then release both buttons. Do not press the SCAN or RDS buttons again ot keep holding them down, other wise the number 1000 will be registered as the first attempt, and you will only have one more attempt to repeat the procedure.
Enter the code number given on the radio card using the station selector buttons 2 to 5 - button 2 for the first digit, 3 for the second and the so on.
Press SCAN & RDS button at the same time again to confirm the code number. The word SAFE will appear in the display
Then release both buttons. A radio frequency will then appear automatically in the display after a short delay. The radio is now ready for use.
Incorrect code number
If an incorrect code number is entered by mistake when reactivating the radio, the word SAFE will start flashing and then appear continuously.
The entire procedure now can be repeated
once again. If the wrong code is entered again, the radio will be disabled for an hour.
After this period (the radio must be left switched on) the number of attempts shown on the display will go off and the radio can be reactivated again as described earlier.
The same cycle of two attempts, followed by a one hour interval, can be repeated again if you find yourself really stupid.
Unfortunately you gotta contact Audi dealer if you don’t have the correct code or have lost it.
Hope that helps.