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Thread: 2012 L96 E78 Cooling Fans PSA

  1. #1
    Tuner in Training DanSchafer93's Avatar
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    2012 L96 E78 Cooling Fans PSA

    Hey all,
    Over the last week or two I have been doing a lot of digging trying to find how to control electric cooling fans with the E78 ECM for a 2012 L96 6.0L LS. Since I have various resources and a LOT of time on my hands due to my job not always being very demanding I figured I would share what I was able to find.

    On the E78 ECM, J1 Connector, pin 54 is fan 1 control and pin 41 is fan 2 control. Under this engine they are not called out as fan control on the list, they actually say not available, and you have to add pins to this location. However I found a thread under a chevy cruze 1.4L turbo, which also is supposed to use an E78, that suggested that these were in fact the correct pins. What I did was found other pins from the list that I knew I would never use, cut the wire so it had a pigtail coming from the connector and just relocated the pin, then butt connected an extension wire out the the pin in the fuse block.

    On the Fuse block with 2012 chevy/ gmc truck, connector x2, Pin A1 is fan control low and Pin B5 is fan control high.

    Also on the fuse block, Connector X1, Pins D1 and C1 are the power circuits that go out to the fans and each fan will need a ground. In the schematic I have attached, it shows the power to the fans wired differently, I did not try that route, but I am running electric fans not Pulse Width Modulated fans, therefore I want them either on or off. Not cycling power or giving varied voltage to the fans.

    Attached is the full pinout that is called out for fuse block connectors X1 and X2. Where they are located on the bottom of the fuse block junction block, the wiring schematic and the J1 connector call out for the E78.

    Please feel free to ask any questions you need!
    Hope this helps some of your builds like it helped mine!
    -Dan
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    Last edited by DanSchafer93; 05-02-2019 at 01:25 PM.

  2. #2
    You got them working!?

  3. #3
    Tuner in Training DanSchafer93's Avatar
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    Yep! Just did final check on it this morning and tie up! I'm so glad to have gotten them working.

    Also, I forgot to mention that in the tuning I had to select discrete as the fan type and I selected 2 fans for quantity. I left the Hertz at 128. If need be I can upload my settings later tonight.

  4. #4
    That's awesome, so many people failed before you and I'm stoked you got it. I'll be putting efans on my '15 within a couple weeks as I'm running with no fans right now �� and I was worried I was going to have to use a hokey pokey universal controller. If you could post the tune, it would be much obliged.

  5. #5
    Don’t try and use spal fans, the relays and wiring can’t handle amp draw.

  6. #6
    Tuner in Training DanSchafer93's Avatar
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    Sorry guys, Had to work on a few other projects around the shop the last week or so to get caught back up. I still am having trouble with the fans kicking on due to temperature so I need to do a little more tweaking to the tune but I will post it as soon as its functional. Still able to kick the fans on with the control panel while monitoring though.

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    Tuner in Training DanSchafer93's Avatar
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    Quote Originally Posted by RySmDPT14 View Post
    Don’t try and use spal fans, the relays and wiring can’t handle amp draw.
    I used a a kit I picked up from Champion radiator. My truck is a 1986 K2500 Squarebody Chevy so I used the radiator and cooling fans from the link. https://www.championradiators.com/3-...o-19-1973-1987. They pull quite a bit of power but as long as you have power to both your power studs everything I read says it should be fine.

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    I could never get mine to work, however i was able to trigger then with hptuners.can you post your e78 file.please

  9. #9
    Tuner in Training DanSchafer93's Avatar
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    Well it would seem I got a little ahead of myself. I found a way for them to either be on all the time, or not at all. I think the logic is broken for the ECT desired %. I can literally set the 0 state to a 1 for fan output 1 and a single fan comes on. If I do this for fan output 2 both come on regardless of what fan output 1 is set to, 0 or 1. It seems to me that fan output 3 does nothing for me but I only have 2 fans wired in place. At least for now, with town driving I just keep fan 2 on all the time and keep my laptop with me since my truck is in the beginning phases of road worthiness. I had to take a break for some time due to getting very ill. Sorry for the delay to all of you guys that were following the thread. I didn't mean to bail on you all. Anywho enough about the sappy stuff, I threw in the tune I have been running currently. The MAF settings have been tweaked since I have a TON of air flow with a cold air intake and Long tube headers and nothing but mufflers. (Catalytic converters are not required where I live). Definitely be cautious if you plan on just throwing my tune on your engine!

    Thanks,
    Dan
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    Tuner in Training DanSchafer93's Avatar
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    I did just read in a different forum for a little older LS2 with the same type of programming type that you need to program it so fan 1 does not come on before 192 degrees. So I changed around my numbers on the desired fan% per ECT and we shall see if that changes anything.... Links I found helpful so far are the following...

    http://www.hptuners.com/help/vcm_edi...ystem_fans.htm
    https://forum.hptuners.com/showthrea...r-lack-thereof

    Thanks,
    Dan

  11. #11
    Tuning Addict blindsquirrel's Avatar
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    Fan vs AC Pressure is 100% in all cells? AFAIK, that table is active even when AC is off, so fans will never be 'off' with it set like that.

    Similarly, in the Fan vs ECT table the first cell of the 190* row is set to 40 (and your Desired ECT table is set to make it use the 190* row all the time, which is OK). First cell HAS to be 0 or else the fan cannot turn off, whether that is in the ECT or AC tables.

    Something looks off in the Output vs State tables as well. Look up some stock tunes that used discrete fans to see how those work.

  12. #12
    Tuning Addict blindsquirrel's Avatar
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    Another thing to try, set DTCs P0480 & 481 to MIL on second error like a stock discrete tune would be. I don't know if having them as No Error will disable some part of how those pins work but it won't hurt anything to have the codes enabled.

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    Was this ever resolved? Would like to know it will work before removing and repining.

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    MExchangeGM SVG Conversion DataBLACK BOX REDOsEnglish-American4499742_svg.png

    the e78 does not use two pins. only pin 41 of the X1 connector. Nor do they use a relay. They use PWM fan motor assemblies. The fan motor gets and power and ground and then the ecm sends on a pulse signal on pin 41 to the fan motors directly.

    That diagram is directly out of GM Service Information
    Last edited by SilverBullet6.0; 07-19-2020 at 07:25 PM.

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    Tuning Addict blindsquirrel's Avatar
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    So how does the '12 Cruze E78 tune file have fan settings of 'Discrete' and 'Number of fans fitted: 2', if there's only a single PWM output going to two variable speed fans?

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    Im not sure. That just how it is set up on a 2017 3500 suburban, so I assume it would be similar to the truck platform. Id think it'd be a straight forward swap to order the fan assembly for the 3500 suburban from a dealer, but it'd be nice to see the tune file for the suburban to clone settings.

  17. #17
    Tuning Addict blindsquirrel's Avatar
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    If the Cruze diagram shows two separate fan outputs, it's a good bet that any other E78 would have that second output pin activated by making the appropriate changes to the tune file.

    There's a 2015 Suburban file in the repository (only one, and it's E92), but '15 and '17 all variants show the same fan assy in the parts lookup, and the '15 Sub tune file uses fan settings of 1-fan PWM EV. They just used different fan hardware and tune settings across different platforms like lots of other ECMs used across multiple platforms.

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    Any update on this? Have a customer wanting to put fans on a 2014 and a 2015 2500HD with 6.0 and E78 but don't want to get involved if it's not going to work with the factory computer.

  19. #19
    Tuner in Training DanSchafer93's Avatar
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    When I was using the E78 ecu I just had to lock both fans on all the time. To the best of my knowledge it's still not fixed. I currently am running a camaro ecu since I have converted my 6.0L to a manual trans. Fans work on the E38 ecu's like a charm.

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    What all was involved for the ecm swap other than o/s and vin update?