Circuit/System Description
WARNING: This page is about a different car, the 2006 Chevrolet Monte Carlo and 2006 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
As the power mode master (PMM), the body control module (BCM) monitors the ignition inputs off/run/crank voltage, ignition 1 voltage and the accessory voltage signals supplied from the ignition switch. The BCM uses the sequence that the signals appear, their voltage levels, the engine run flag (ERF) status and the remote start status to determine the power mode.
When the ignition switch is placed in the RUN or CRANK position, the switch supplies B+ to the BCM ignition 1 voltage input terminal. If this circuit becomes shorted to B+, ground or the circuit opens, DTC B1370 will set.