2014 Audi rs7 added second key through obd in around 10 minutes, Autel IM608 asked me to do energize the BCM and that slowed me down a bit. Im608 is nice.
It is the smart key with comfort access. It was a used key, but wiped from the company I purchased it from.
Here’s the tips on programming key on this car via OBD.
I unplugged the car battery when asked me to do it, because first time doing it in 7 series and didn’t know where the bcm2 was and that did the trick.
So I didn’t need to unplug BCM2, just unplug battery.
Some people say have to unplug the bcm2 otherwise it will lock the gearbox. I have ODIS so not too worried.
My friend corrupted bcm2 data oon a Audi Q5 2012. Autel asked him to de-energize bcm2. He disconnected all plugs and car was dead after that. He needed to read it on bench and send dump to repair guy to fix data. Everything was ok after repairing dflash. Then successfully added 2nd key.
Maybe weak battery or some voltage drop.
I did it in 2 cars so far using im608 without problems, including an A8 D4, but again odis is here to help with component protection if that happens.
Hope it helps.