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Thread: LQ4 PCM cooling fan control

  1. #1
    LQ4/LS1 Turner's Avatar
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    LQ4 PCM cooling fan control

    Wow I haven't been on here in ages. Truck is still running like a hot damn, kicking the ass of many poor bastards haha. I'm having a problem getting my fans to be controlled by the PCM tho. For those of you who don't know, it's a 05 LQ4 (with some goodies) with a 04 PCM. I can manually turn either fan 1 or fan 2,3 on and off with my scan tool, but they wont turn on by themselves at the 215F they're set at. Any other people on here with LS swaps have a idea? I've been using a flex-a-lite fan controller, but it just crapped out and I don't wanna buy a new one if I don't have to. Thanks.

  2. #2
    I'm BATMAN! Harley's Avatar
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    Are you actually seeing 215F? Can you verify that the PCM temperature and controls are set correctly? Not set to 215C? It's been awhile since I played around retuning PCMs, but I remember that with some functions you had to both set the temp and turn on the function to get them to activate.

    The low speed control should come from the Blue Connector pin #42 and the high speed from the Red Connector pin #33.
    Black 'n Tanazer, Long Bed, Coupe Quattro, Old Caddy, Old Rice

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  3. #3
    LQ4/LS1 Turner's Avatar
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    ya everything is set up properly. i have let it get to 225f while watching the ect on my scan tool and still nothing. i can control them with the scan tool on and off, but they wont work with engine temp. i made sure he didn't set them in C by accident, says he didn't. i am thinking he missed turning something on, i will give him a call a bit later. thanks

  4. #4
    5.7L VORTEC 350 blazin4low's Avatar
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    I'm trying to wire my fans for pcm control, you have the relay and wiring diagrams handy by chance?
    http://i158.photobucket.com/albums/t114/VortecBlazer/sidredo.jpg
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  5. #5
    LQ4/LS1 Turner's Avatar
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    Thats the diagram from a 2005 chev truck. PCM grounds low speed fan on connector 1, and high speed on connector 2.


  6. #6
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    Turner, I'm a big fan of your truck and it was motivation for me to finish my Blazer. Just wanted to let you know.

    You may have already done this but did you check the vehicle speed turn on and off settings? From what I remember they cut off over a certain speed. The wiring is right if you can turn them on and off with the scanner so it must be in the tune somewhere.

    I'm running camaro fans in my Blazer and it uses three relays similar to what you posted but wired a little different.
    Last edited by Steves2Door; 09-11-2014 at 02:52 PM.

  7. #7
    LQ4/LS1 Turner's Avatar
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    oh nice, thats cool. i love the entire setup in my truck. ya can cruise around with super smooth shifts like grandmas buick all day, then when ya wanna have some fun you can blow the tires off into third gear haha. ya i figured its probably something like that, didnt feel like bothering with it tho so i just got another controller. maybe this winter ill look at it.

  8. #8
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    Yeah you can't beat these engines in these trucks...

    I was following your thread because you were the only one I could find that was trying a 4X4 frame but then you switched it on me haha.

    Here's a couple of pics if you're interested

    http://www.s10forum.com/forum/f213/1...t-56-a-519363/






  9. #9
    LQ4/LS1 Turner's Avatar
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    oh nice, looks awesome. i love the looks on peoples faces when i open the hood and they're expecting a 350 or something haha

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