Battery Cooling Fan Inoperative

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by CSTP, Mar 16, 2024.

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  1. CSTP

    CSTP New Member

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    Hello! New here!

    I have a 2008 Prius that recently pulled a Red Triangle of Death on me. I hired a mobile battery replacement tech and had it replaced. After driving for about 30 minutes the triangle came back on. I parked the vehicle and got to work on figuring it out. The code that came up is Cooling Fan Inoperable. Makes sense as to why the only battery died.

    Only thing is, when I use my Autel to run the fan through the hybrid battery function it tells me that the ECU does not support it.

    I have identifix, And I have been through a lot of the steps to troubleshoot this error. The one tool I do not have at my disposal is a Oscilloscope to test the ECU with.

    Also, things melted? Pics for reference. All of these wires and connectors are near the door control receiver. The white and black wires are grounds.
    WhatsApp Image 2024-03-16 at 3.56.10 PM.jpeg WhatsApp Image 2024-03-16 at 3.56.09 PM (1).jpeg WhatsApp Image 2024-03-16 at 3.56.09 PM.jpeg
     
    #1 CSTP, Mar 16, 2024
  2. Tombukt2

    Tombukt2 Senior Member

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    This is in the trunk near the battery cooling fan show me the cooling fan and it's a little plug the white one and all that in the right side rear quarter just forward of the 12 volt or above the 12 volt All of that is right there I'm not sure where all these wires that are burning are are in relation to what's not working The black box with the red label it's not real familiar to me because they probably never get touched or worked on I realize what it is but this should be an indication of what caused that to burn up somewhere near the stuff back there whether they were sitting against something that was getting very warm which I can't imagine what that would be your battery and modules are covered with a case etc.
     
    #2 Tombukt2, Mar 17, 2024
  3. CSTP

    CSTP New Member

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    Yeah so these burnt wires are on driver side in the trunk. I checked that the fan operates when power is applied, the 1 and 2 pins in the battery connector have continuity between the 3 and 4 pins of the temperature sensor in the airway (not sure thats what it's called). I have not been able to see continuity between the battery computer connector and the 2 pin connector at the fan. Which led me to remove the panel at the driver side read and discover the melted mess behind it. So i went looking for a replacement harness but I cannot find any parts diagrams to help me locate the part number. Thinking about applying a switch, lol.
     
    #3 CSTP, Mar 17, 2024
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    The most common cause of battery fan problems is corrosion at connector BM1 due to body seam leaks around the tailgate.

    While the battery ecu does monitor fan negative as a feedback, it controls that negative side via a motor controller (transistor).

    Fan positive goes through a relay (ecu controlled - is the blue cube in the picture) and doesn't go to the ecu.

    The brown, violet, and yellow wires go through BM1 to the ecu.

    Screenshot_20240317-212256.jpeg Screenshot_20240317-213122.jpeg

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Mar 17, 2024
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  5. CSTP

    CSTP New Member

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    Interesting, I DID have a major water leak and noticed corrosion on this connector. that was where a lot of online videos pointed to, so that was the first place I checked, I guess I should have mentioned that. I removed the connectors and wired them straight to one another. Still having this issue...
     
    #5 CSTP, Mar 18, 2024
  6. mr_guy_mann

    mr_guy_mann Senior Member

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    What model Autel scantool? It might "disallow" the test if the ecu sees a fault with the circuits. I can unplug the fan but it won't set a code until it tries to turn the fan on.

    Clear the code and use a DVOM to check for 12V power at the fan (light green wire) or the fan control module while commanding it on with your scantool.

    Posted via the PriusChat mobile app.
     
    #6 mr_guy_mann, Mar 19, 2024
  7. CSTP

    CSTP New Member

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    I am using a MaxiCOM MK808S.
    I have a fleet of cars for my company and about 8 of them are Prius, and I can command the scan tool to operate all of the fans in the other Prius, however this one comes back with "ECU Does Not Support this Function."
    So are you saying that I should put it all back together and run the car until the fan temp "should" turn the fan on, get the code to come up, clear the code, and check again if I can command the function? I actually have not tried this.
     
    #7 CSTP, Mar 19, 2024
  8. mr_guy_mann

    mr_guy_mann Senior Member

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    I would connect the voltmeter for testing, clear the code, and then attempt the scantool bidirectional command. It's something to try. (Getting the battery warm could also work, but can take some time if it's cold out).

    I have not seen "this test not supported" for the fan on a Gen2 before. If your scantool works on other Gen2s, then it "should" work on this one.

    The whole idea it to get the ecu to (try) turning the fan on so you can do more testing. AFAIK the ecu won't energize the power relay until it's also sending a pulse width modulated command to the fan module.

    Posted via the PriusChat mobile app.
     
    #8 mr_guy_mann, Mar 20, 2024
    Last edited: Mar 20, 2024
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