How To Program Audi A6 C5/ A4 B6 Key! Might work on other cars.
Hello, today I will show you how to reprogram or resynchronize your car key if it stopped working after you changed the bateries in it.
First, put one key in the ignition and turn the ignition on and leave the key in the ignition.
Second, get out of the car, close the door and lock your car with you second key from the outside.
Third, remove the key from the door and press two times on the unlock button (you will see your blinker blink) and wait around 10 seconds.
Four, after waiting 10 seconds, press on the unlock button again (the car should unlock), then take out the key that was in the ignition and try your key.
Congratulations! It's that simple! Thanks for watching!
This is Audi A6 C5 (97-04)