Conditions for Setting the DTC
WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
DTC B257C 00
The headlamp control module receives a serial data message from the left headlamp internal logic module that an internal headlamp malfunction has occurred.
DTC B257D 00
The headlamp control module receives a serial data message from the right headlamp internal logic module that an internal headlamp malfunction has occurred.