Originally Posted by arsevader
Some cars in the past used the main brakes as the emergency brake. This isn't the case with BMW, they all have separate parking brakes.
The fluid check advice is good though.
That doesn't have anything to do with which warning light would come on.
It's very likely it could be low fluid level, if the switch itself hasn't malfunctioned.
If your car has an OBC it will also tell you CHECK BRAKE FLUID, but not all models have it.