http://64.91.234.154/coppermine/albu...k_Sep_2004.pdf
Unless things have changed since 2005 the Regulated Voltage Control System is apparently not used in trucks with a GVWR greater than 8600lbs. All 2500 and 3500 diesel trucks exceed this GVWR. The manual doesn't say this and the GM Bulletin doesn't specify what they mean by light truck.
Sorry randye I wasn't looking at other makes. Your manual may give you some idea, but as seen in the case of the GM manual it isn't a sure thing.