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.
P257D
The engine control module detects a plausibility error between the observed hood ajar position and the reported hood ajar position.
P257E
The engine control module detects a short to ground in the hood ajar signal input to the engine control module.
P257F
The engine control module detects a short to voltage or an open/high resistance in the hood ajar signal input to the engine control module.