Alternator Sub Harness: There are only 2 popular option for the Alternators used on LS applications. The standard 4-pin alternators were used on most everything up until 2005. In 2005 you could have either the 4-pin unit, or the new Bosch 2-pin alternator, which has it's own computer, known as a GBCM (Generator Battery Charge Module). To use this 2-pin alternator, the GBCM will need to be used. This is located on the main NEGATIVE battery cable, right at the battery. It will have an amp-clamp built in and the negative cable runs through it. Our integrated harness will plug directly into the GBCM, and an adapter is used at the alternator for correct connection. If you are using the 4-pin alternator, a bypass plug is used on the GBCM connector that allows the correct signal to reach the alternator. Both units are plug and play.