Especially in damp climes, but even in dry ones, the vast majority of problems I've had with SRS faults turn out to be related to dirty plugs and connections. I'm not sure where the lines run on the 700. On the 2 series, the harness runs from the ECU under the driver's seat up the left side of the center dash console where you'll find the yellow plug that is the usual cause. I've also fund dirty plugs at the airbag itself to be the problem. High resistance, no doubt. Sometimes I've been able to clear the fault after simply by unplugging the one next to my knee and plugging it back in, then running the clear code routine. Or, you may have a bad SRS ECU.