Okay, ended up replacing the alternator and all seems well, except for the pesky ESP/BAS light.

Traction control works, though I'm not sure about stability control. Not sure about ABS, but all fuses appear to be in-tact.

The BAS/ESP light doesn't come on it seems (need to do more 'testing') until I goose it, then traction control stays on and I can't turn it off until an ignition cycle.

Any way to tell for sure that it's the yaw sensor?