If you still believe the BCM is damaged you might want to look around the BCM for moisture, indicative of a plugged plenum drain under the passenger side cowl. When those plug up you can get water intrusion in the cabin which can damage the BCM. If the water intrusion is recent it might not have an odor yet but if you peel the passenger carpet back you can feel it on the floor board.
Is there a module in the trunk called BCM? I read on some mustang forums that the passenger module is the smart junction box (sjb) and the BCM is in the trunk?