hello
sometime back i put an electric fan on my '99 GMC nbs 5.3L . i am now in the procesess of learning to tune. i want to run the fans from the pcm it does support it. problem is i do not know which pins it enables as there are 30 of them not in use.
anyone been down this road before?
thanks

 

pin 42

 

what work truck said, pin 42 runs the fans

 

hey guys thanks for the reply. i asume thats on the c-1 blue,cause it's busy with the trans on the red one.
the def file does support two fans so there must be one other ground pin.
c-1#42 runs f-body low speed, same pcm differnt program as f-body uses c-2#33 for high speed, trucks use it for the recirc on hvac. i really apprieate the help. if there is there is the second pin i'm gonna find it.
i have a two speed fan set up off a crown vic, works slick but i know alot you you belive i'm going to hell because of it. won't happen i never drive it on sunday

 

not to be a turd but i know you can search and find exactally what you want

 

i don't smell any turds and i'm pretty close, right across the river from you.
i spent a couple hours searching the fan threads and found that '03 &'04 use 33 and 42 pins. the '99 - '02 use 42pin. there are a few threads like mine asking the same question with no answer. tuner cats does support 2 fans on '99 - '02 but the posts from people that got nelson tune and harness for these trucks only use pin 42 if he could sell a two speed harness setup i'm sure he would.
thanks to all who replied