Circuit/System Description
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.
The power supply transformer is used to boost battery voltage to sensitive loads during engine restart. It provides two voltage outputs that provide the boosted voltage. The power supply transformer communicates to the ECM. When the engine is not cranking, the power supply transformer passes through voltage from the two supply circuits. The ECM receives data about the sensed output voltages provided by the power supply transformer.