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I tried to connect my lt1 fans to my pcm, but I don't know what pins to use. I have a pcm pin readout for my truck but it does not list any pins for fans. Are the pcms different for 2wd and 4wd. I was told that blue42 was for low speed fan and red33 for high speed fan, but my pcm shows blue42 not used and red33 recirculation actuator control. I'm confused on which pins to connect my relays to. Could someone help me out?
Jared
01 Z71 4wd
i used the blue 42 pin on the connector. look on the passenger side of your truck and find a connector that isn't being used, now trace it back to the pcm.
Remove it from the pcm. To do this:
(this is all from memory)
- disconnect your battery
-remove the two bolts holding the pcm connectors on the pcm
-pull off that gray cover the is ontop of the pins.
-remove the blue plastice piece that is holding the connectors in
now take that wire you found earlier and stick it in the blue 42 connector. you're going to need edit to adjust the fan control to say 185deg. stock is set way high like almost 300 so it never comes on. once that is done, connect your wire to the relay.
I'm pretty sure it's pin 42, if you looked for the other pins and they are used, then don't use them of course, I have a z28 pcm , but a truck harness. So, i had to install a wire into the blue 42 spot, i simply used one of the connector wires that weren't being used.
hope this helps, post away, i'll be watching, until 5pm and then later on tonight.
until then, if you need the fans, just install a toggle switch that grounds the signal wire, then your fans will come on.
btw, this is exactly how i did mine. http://www.ls1truck.com/reference/articles.html
later,
allen
thanks for help.
are you sure that blue 42 is the right pin for my truck because my readout does not say anything about electric fans? Also to find a connector not being used should i just look at my readout and the pcm and find a wire that is not used by my pcm? this electrical stuff is confusing to me.
Thanks
Jared
since your truck came with a clutch fan, you won't see anything about an electric fan control on the truck pcm. it's in there and you just have to find the right pin, like we both think it's blue 42.
i know on the trucks, there are some or one connector that is not used, kind of hanging there on the passenger side of the engine, i'm not sure if that goes to the pcm or not, but it's worth a try to find out. that way you have a wire inside the harness and you can easily pull it out of the pcm and put it in pin 42. then cut the connector off and attatch it to the relay. that's how i would do it, this is just a suggestion.
if the connector doesn't go to the pcm, you'll have to tap into the pcm somehow, i know napa sells the wire and connectors.
hope you get it done, i'd like to see it work, not as much as you though,
let me ask: would you have bought a setup that all you have to do is to supply power, and screw the relays onto the engine bay somewhere, and it would have a wire supplied to tap into the pcm, just wondering if it would be worth it to make some harnesses, man all these ideas and not enuff time.
allen
i think i understand now. thanks. ill let u know how it goes.
i would definately buy the preassembled wiring. thats a great idea.
Jared