Circuit Description
WARNING: This page is about a different car, the 2002 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
The BCM uses a input from the ignition switch to determine the power mode that the vehicle is in, this input is ignition 1. When the BCM senses that ignition 1 is inactive when ignition 0 and 3 are active and the engine is running, DTC B1374 is set.