5.3 wiring question
http://www.lt1swap.com/2004vortec_pcm.htm
it shows the gray wire on port 75 of the ecu on the green bundle and most alternators are one wire arent they?
LS1's used a single RED wire in a 4 position plug as pictured a few posts above.
Vortec 4.8/5.3/6.0 series used sometimes a single brown wire in the same location as the red above, and sometimes 2 wires, brown and gray. - 4 position plug.
Around 2005 or 2006 on the Vortec trucks, the PCM no longer connects to the alternator on some vehicles, and now there is a generator-battery control module, or GBCM for short. This monitors current draw on the negative battery cable, and controls the alternator its self. These alternators had a narrow 2 pin plug with two wires, gray and brown.
I have seen in some late model harnesses a 3rd blue wire, unknown what it is for, as it does NOT go to the PCM.
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