There should be a switch under the brake pedals. Could be gone. just needs
replacing.

Common problem for the 3 series is the electrical wire bundle that runs from
the rear electrical lights up through the left-side trunk water drain
channel to the trunk lid. The opening and closing of the trunk lid bends the
wire bundle and weakens it to the point of wire insulation breakage...this
can cause many electrical problems, include fire.  You had better gently
pull out the rubber retaining grommet on the trunk lid that surrounds the
wire bundle and carefully cut open the plastic bundle wrap as much as
possible above and below where the wire bundle has been bending. I bet you
will find broken insulation, bare exposed wires, and maybe even broken
wires.  I repaired my wires and used heat-shrink wrap, then closed up the
bundle wrap and used electrical tape to close up the bundle wrap. Re-install
the rubber grommet, then make sure the wire bundle sits in the bundle
retaining clip which is on the trunk hinge...this will keep the wire bundle
off the bottom of the water drain channel, so will keep the bundle dry.....I
recommend you check this wire bundle ASAP, because of the fire hazard
potential.... and it will probably solve any electrical problems you may not
be aware of. It's an easy fix, and cheap, too.

Good luck