Code B1000, air bag light, other symptoms?

Symptoms include the airbag light comes on and stays on immediately after clearing BCM codes. BCM throws code B1000 immediately after clearing. No other codes ever pop up, even after months (except p0446 in the ECM). I swapped the BCM with a tested used good one (same part number) and ran the 30-minute passkey relearn procedure. No change.

The previous owner has clearly been messing around. They've bypassed the horn and put in a crappy button and weak sounding horn which makes proper road rage impossible to achieve. And the car will randomly pop the trunk. Even when I'm driving 70mph I'll hear it. It is one of the few Century Customs with a trunk pop button and a key fob.

Fob works btw. As do its functions. After getting rear ended by a guy in a full-sized van awhile back, I want working air bags. He destroyed his front end btw and I can't find a scratch on this car.