Hello!
I used the search function but didn't find anything useful except for a link, which unfortunately is only written in English.

I myself can barely speak English, and it's difficult for me to understand because of my deafness.
I have an AUDI Cabriolet, manufactured in 1999, with the engine code AHU. MSTG.
028906021GC 1.9L R4 EDC G00SG 1408
Encoding: 00005 WSC: 00672
4B0953234 IMM0 AUZ9Z0X3031132 D03 WFS
Coding: 00000 WSC: 00000
from a friend whose second key had been gathering dust in the key cabinet for about 4 years, which the WSF no longer recognizes!

The remote control works perfectly fine despite not being used for 4 years

because the battery is still not empty!
Wie Lerne ich den 2. Keys in?
I have the VAG 1551 test device.