D91DE6 is a fault stored in your BMW's memory (an ISTA fault code, not a standard OBD-II P-code).
What it means: Missing 'status outer light, front electronics 1 right' message — receiver FEM/BDC, transmitter TMSL (right headlight driver). Effectively a loss of communication with the right front lighting module; common cause is a corroded connector, moisture or a failed headlight driver module.
