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    1. #1
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      Sep 2005
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      Fans run constantly Ls3 with Psi harness and ecu.......

      Ls3 running a Psi harness and ecm, and the output to each fan (almost immediately after the car starts) supplies negative regardless of engine temp. The odd thing is, when a Power Probe is connected to the fan trigger wires from the ecm, it's not a consistent negative output, but broken up....kind of like -----.-..-..-...-------.-.--. It is enough to energize the relay and run the fans. I need to button it up and move the car. This is the second ecu from them and the issue is still present. Any help would be greatly appreciated.
      1971 Firebird
      2017 Slipstream SS

    2. #2
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      what ecm is it using and what connector and pin is the wire going to on the ecm?..... almost sounds like a pwm signal for the fans

    3. #3
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      It is the E38. It's hard to tell where the wires go as they are bundled into the harness. Is pwm possible for this ecm? I've just triple checked all connections throughout the harness and everything seems tight, correct and unbroken. A scanner shows the temp slowly climbing, so I believe the temp sensor is working correctly.
      1971 Firebird
      2017 Slipstream SS

    4. #4
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      Yes, the E38 can do pwm for the fans, I am pretty sure though most tuners will set the duty cycle to 100% and then it is simply an on/off (I assume)... I'm no expert on the subject and am still learning the in and outs of how all this stuff works, but might be worth talking to whoever did the tune on the ECM and find out what its set to.

    5. #5
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    6. #6
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      That definitely sounds reasonable. I'll have to see what Psi says. Thanks so much for your help.
      1971 Firebird
      2017 Slipstream SS

    7. #7
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      hope that's the problem.... gl

    8. #8
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      Jan 2013
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      Yes, the software in the E38 ECM needs to be set to the discrete mode for the fans. You may also want to change the temperature settings if they are the stock ones.

    9. #9
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      Mar 2014
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      A friend of mine had this happen with a motor from Turnkey, it was something in the computer that malfunctioned and he had to send it back to fix the problem.
      Nelson
      1969 Chevelle "Cone Smasher" Family Project
      https://www.pro-touring.com/threads/...uot?highlight=

      1984 "Rustang" GT, 5.0, 5 Speed Project
      https://www.pro-touring.com/threads/...T-(Slow-Build)

    10. #10
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      Thanks for all the replies...I'll contact them this morning to see what they say. I'm hoping that's the problem.
      1971 Firebird
      2017 Slipstream SS

    11. #11
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      I was told everything is set correctly. I have no idea what else could be causing these issues.

      1971 Firebird
      2017 Slipstream SS

    12. #12
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      Quote Originally Posted by cpd004 View Post
      I was told everything is set correctly. I have no idea what else could be causing these issues.

      Hmm, this is more of a question than an answer.....

      I see "fan type" is set to "Discrete". but shouldn't the "Fan Desired" be set to 100% at 217 and above? if you wanted 43% fan I would think that it would have to use pwm to achieve that, anyone with experience with HP tuners want to chime in one this?

    13. #13
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      Quote Originally Posted by ChevelleNV View Post
      Hmm, this is more of a question than an answer.....

      I see "fan type" is set to "Discrete". but shouldn't the "Fan Desired" be set to 100% at 217 and above? if you wanted 43% fan I would think that it would have to use pwm to achieve that, anyone with experience with HP tuners want to chime in one this?
      Yes, he needs to post those charts as well. Also he needs to post what temperatures he wants the car to run at.

    14. #14
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      That's the only thing I was sent from them.

      I was told the tuner didn't tune the ecm correctly once again, so back it goes.
      1971 Firebird
      2017 Slipstream SS

    15. #15
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      The same issues are still present with the retuned ecm. Here are the settings:



      If anyone has any ideas or sees any issues with the settings that would cause the fans to run constantly, please post.

      I posted this new info here because of the previous posts.
      1971 Firebird
      2017 Slipstream SS

    16. #16
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      For us to help we need two pieces of information. You are indeed running two fans, correct? When do you want the fan(s) to come on and off.

      What you have in the engine coolant temperature chart is wrong and is your problem. In the fan transition chart you have the one fan turning off at 25 ( 1>0 ). In the other chart you have 40 posted in the 192 degree chart. It will never turn off. That number needs to be below 25.

    17. #17
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      This is what it is supposed to be set at per the instructions:

      If PSI programmed your PCM, your fans will be
      set to come on at 182 and 192, respectively.

      I am running two fans controlled by relays wired as shown on Page 11 of these instructions:
      http://psiconversion.com/tech_articl...structions.pdf

      1989GTA, thank you for taking the time to help me out with this.
      1971 Firebird
      2017 Slipstream SS

    18. #18
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      Lets take this a step at a time. Look at your fan state transition chart. 0>1 is fan one turning on. You have 50 entered in that spot. So anything above 50 will turn fan one on. Now look at 1>2 that is where fan 2 will turn on. So anything greater than 90 will turn on fan 2.

      On the same chart look down at 1 >0 this is where fan one will turn off. You have 25 in that spot. Look at 2>1 that is where fan two will shut off. You have 50 in that spot.

      Now lets go look at the engine coolant temperature chart you have posted. As you can see 192 degrees is as low as that chart will go. So with the software you have that is the lowest a fan will turn off. If I am reading things correctly both your fans are going to turn on at 196 degrees. Now you have a 40 in the 192 slot. Fan 2 "should" turn off as that is below 50 but fan one will keep running until the ignition is shut off as 50 is greater than 40.

      So in order to keep the fans from running all the time you need something like fan one coming on around 202 degrees and shutting off around 192 degrees. So you need like 48 in the 199 slot and 52 in the 203 slot. You will notice that there are 4 numbers between the 48 and 52. You have 50 in the other chart so I split it. So your fan will come on halfway between 199 and 203. Hope that makes sense.

      Now for fan two to turn on maybe have it come on around 212 degrees. So at the 210 spot enter 88 and in the 214 spot enter 92. Again you will notice that 212 is split between 210 and 214. You will also notice that 90 is split between 88 and 92.

      The slots in 207 and 210 need to be less than 90 but above 50 the shut off number. So put 88 in those slots. To shut off fan two around 202 degrees or so. So you already have 52 in the 203 slot so fan two will shut off when the temperature reaches that point.

      Now the 199 slot needs to be less than the 50 but above 25. So maybe enter 47 in that slot. Maybe 30 in slot 196 and something less than 25 in 192 slot like a ten. I don't have mine set up that way so you may have to play with that number. I have a 0 in the 192 slot.

      You can play with these numbers some to get the desired fan operation you are looking for. I hope this has been of some help and maybe some others can make some comments in case I overlooked something.

    19. #19
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      1989GTA, thanks for the explanation. While I'm still a bit confused, it is getting clearer.

      Fan State Transition Desired % (where the 50 is) is where the fans turn on and off (if I understand this correctly). The 50 represents 50% of what exactly though?

      1971 Firebird
      2017 Slipstream SS


    20. #20
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      Here is an explanation I found for the discrete mode.

      "So, what GM did is make the first fan "on" correspond to the PCM requesting "50% fan", and having it stay on until the PCM was down to wanting "25% fan". The 2nd, larger/faster fan works in a similar fashion ... on at "90%" and off at "50%"."

      I think your problem is the engine coolant temperature chart is screwed up and hard for you to make a visulazation. I will look and see if I can find one that is done correctly and post it. Things should become more clear to you at that point.

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