There is so many parts to the SRS that can trip the light. I agree that the contact rings in the steering, known to me as a clock spring in other cars, can go bad since they are the only wearable part in the system. Everything else is static.

With that said, you may want to look under the seats. Each seat has a connector for the SRS. If its not connected, you will get a code. I believe its a connector for the seat belt clip. And if I recall right, each end is red so its hard to miss.

After that, it really could be any number of connectors. Assuming you checked fuses first.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car