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 B258C 00
The headlamp control module receives a serial data message from the left headlamp ballast that a malfunction has occurred with the ballast or the low beam headlamp.
DTC B258D 00
The headlamp control module receives a serial data message from the right headlamp ballast that a malfunction has occurred with the ballast or the low beam headlamp.