Circuit Description
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The purpose of the accessory power module (APM), integral to the starter/generator control module (SGCM), is to control the amount and direction of energy flowing between the 42v DC and 14v DC Buses via the APM, bi-directional 42v DC to 14v DC converter. During all of the APM functions the voltage is closely monitored between the internal voltage and the 12-volt underhood battery for voltage correlation faults.