I'm re-building a wrecked '08 535xi and needed to replace the battery terminal before having the new DME programmed. I'm not sure if it's neccessary but I know that the programming sequence will abort when it sees that the airbag fault can't be cleared. A wasted trip to the dealer ($$)
The Safety Gateway Module (SGM) looks for a certain resistance across the wires leading to the Safety Battery Terminal. A post on "1 Addicts" (or something like that) mentioned 2-4 ohms. I tried that and it worked. Actually I replaced my deployed cable with a $30 one for an older vehicle but it didn't work. It measured 0.1 ohms across the terminals. I plan to experiment and find what is the minimum resistance allowed by the SGM and add that to the circuit ot the cable. For now though I just have about 3 ohms connected across the plug without actually connecting it to the cable. The SGM is just fine with that. It saved me $250!