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 B2570 02
The BCM detects a short to ground in the rear compartment courtesy lamp control circuit.
DTC B2570 04
The BCM detects a short to voltage or an open/high resistance in the rear compartment courtesy lamp control circuit.