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Thread: Gmpp controller wont shut off cooling fans

  1. #1
    Tuner in Training
    Join Date
    Dec 2012
    Posts
    11

    Gmpp controller wont shut off cooling fans

    I have installed the gmpp ls controller to my lq4 6.0 engine in my 71 chevy truck with a 700r4 transmission. I am having issues with the cooling fans staying on after they turn on due to the coolant temperature. If I drive the vehicle over 25 mph the fans will stay on. I understand that the gmpp ecm requires the vehicle to travel 25 mph and reach the fan "turn off" coolant temp in order for the fans to be commanded off. The problem is that the 700r4 transmission does not have an electronic vehicle speed sensor it is cable driven. . If the vehicle sits and warms up, the fans turn on (as they should at 221f) but will not turn off. My coolant temperatre gets much colder than operating temperature (175f). if i cycle the key the fans stay off until the coolant temperature reaches the threshold to turn them on. It seems like there should be a parameter for vehicle speed and delay relating to the enabling or disabling of the cooling fan. Is there a patch to correct for this missing parameter?

  2. #2
    Advanced Tuner
    Join Date
    Jul 2013
    Location
    Clear Lake tx
    Posts
    423
    There are alot of threads on this issue. Use search topic site:hptuners.com on google or search engine of choice and you should find a quite a bit. I cant tell you from experience but what i have read in short is that its due to not having a wheel speed sensor which i see in your op you know already. That pcm needs one otherwise fans wont shut off. in searching the forum you my find other ways to get a speed sensor wired in.
    Last edited by JBZ; 09-01-2016 at 07:06 AM.
    2010 CTS-V A6, Airaid CAI, 2.4 pulley, ported ls7 throttle body, ID850s, ARH 1-7/8" headers and X pipe, TR7IX plugs, MSD wires, Elite catch can, ZL1 lid and Track Attack HX