Conditions for Setting the DTC
WARNING: This page is about a different car, the 2017 GMC Acadia. However, it is still accessible from the selected car via links, so may be relevant.
P257D
The hood ajar switch signal 2 voltage as measured by the Starter/Generator Control Module is not within a valid voltage range.
P257E
The hybrid powertrain control module 2 detects a short to ground in the hood ajar signal input to the Starter/Generator Control Module.
P257F
The hybrid powertrain control module 2 detects a short to voltage or an open/high resistance in the hood ajar signal input to the Starter/Generator Control Module.