Legacy Mode is the earlier version of the Key Learning function and it keeps all the capabilities needed for older vehicles: erasing all transponder keys, programming a key, reading and writing the mechanical key number. All of it over OBD.
Required licences
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Hardware / cables
AVDI
⚠ WarningErasing the transponder keys does NOT erase the remotes already programmed to the car. After a full erase you will only be able to re-program the keys you physically have in hand, so make sure you have collected them all before you start. On top of that, only one key is programmed at a time: for two or more keys, repeat the procedure.
Procedure
Connect the AVDI, ignition ON, open the Opel/Vauxhall software and start "Key Learning" from the "Special Functions" list, then switch to "Legacy Mode".
If you need to erase all keys (lost or stolen key) press "Erase Transponder-Keys": every transponder key is erased, but the remotes are not.
Gather every key that has to stay working: after the erase you can only re-program the ones you have in front of you.
To program a key press "Program Transponder and Remote Key": you can program brand new keys or re-program keys that already belonged to the same car and were erased.
Program one key at a time; if two or more are needed, repeat the procedure for each one.
To read the mechanical key number press "Mechanical Key Number": on Astra H, Corsa D, Vectra C/Signum and Zafira B you first have to enter a valid Security Code, on the other models it is not required.
To write a new mechanical key number, type it into the edit box and press "Program"; if the security code is required, a message will prompt you to enter it first.
Close the function, cycle the ignition off and on, and try every key for cranking.
Reference screenshots
Source: Manuale Opel/Vauxhall (anche Buick/Cadillac/Chevrolet/GMC), cap. 3.2.1 e 3.2.1.1 (p.18-19) · ⏱ estimated time 30-60 min