D357A5 is a fault stored in your BMW's memory (an ISTA fault code, not a standard OBD-II P-code).
What it means: Front brake-cooling air flap: invalid signal (status) — the DSC can't read the position of the electric actuator that opens/closes the active grille/brake-cooling shutters. Causes: failed/stuck actuator motor, damaged or corroded LIN wiring, or flaps physically jammed by ice/snow/debris.
