Circuit Description
WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) monitors the battery voltage through the battery positive voltage circuit. If the BCM senses that battery voltage is outside of its normal range for 1 second, DTC B1420 will set.