Locating Battery Blower relay

Discussion in 'Gen 2 Prius Technical Discussion' started by harryarcos, Jun 18, 2021.

  1. harryarcos

    harryarcos Junior Member

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    I have P0 P0A84 fault on my 2004 Prius and after looking through many posts on here, am having problems finding the Blower relay. My Engine Room Relay Block looks nothing like that on the workup sheet kindly posted by SFO and is located just below the windscreen wipers. It is 190 x 45 mm and contains just 2 relays with no info. as to what they do.
    Any advice, much appreciated.
     
  2. TMR-JWAP

    TMR-JWAP Senior Member

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    If you're looking for controller stuff and relay stuff for the HV battery, you're about as far away from it as you can possibly be.

    The controller for the HV battery fan is located in the bottom air duct which is located between the bottom passenger side of the HV battery and the car chassis side vent located directly in front of the 12v battery. The controller is on the back of the duct tucked out of the way. The relay is located above the upper duct.

    HV Battery stuff.jpg
     
    #2 TMR-JWAP, Jun 18, 2021
    Last edited: Jun 18, 2021
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  3. harryarcos

    harryarcos Junior Member

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    That's great, many thanks. Chances are that it is a corroded connection, as I had the water in the tyre well problem a few months back. I was taking what I thought was the easy route of checking the fuse and relay first, before taking out the panels, but looks like I need to do that anyway!
     
  4. harryarcos

    harryarcos Junior Member

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    Unfortunately there was no corroded terminal, so I am gradually working through HB - 45 with everything OK. I am unable to check the blower motor controller as I do not have page HB- 159 which it refers to, so if anyone can help, it would be appreciated. Also, can anyone tell me where the battery ECU is located?
     
  5. TMR-JWAP

    TMR-JWAP Senior Member

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    Battyery ecu is inside the battery, on the driver side electronics section
     
  6. davecook89t

    davecook89t Senior Member

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  7. davecook89t

    davecook89t Senior Member

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    More: Prius Gen 2 Manual, Page HB-160.JPG Prius Gen 2 Manual, Page HB-160.JPG Prius Gen 2 Manual, Page HB-161.JPG Prius Gen 2 Manual, Page HB-162.JPG
     
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  8. harryarcos

    harryarcos Junior Member

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    Thanks for the info. but I am getting even more confused. Perhaps there is something on the proceeding page, but I cannot see how there would be voltage between terminal 1 (GND) and body ground as described in the first test (7) ?

    I do not seem to be getting anywhere with locating a fault and perhaps I should have described the full event, because I may have gone totally in the wrong direction. It started on a hot day when I drove the car without any problems and parked it in the sun for about 2 hours. When I then started the car, the red triangle appeared along with VSC, brake warning light and ABS. The fluids were OK and the brakes worked, so I continued using the car and the following day, all the warning lights were gone. A few days later exactly the same thing happened, so I dug out the OBD11 and Techstream which I had not used for a couple of years and found the following current DTCs: P3000, P0A84, B1421, C2310 and C2318 There were historic DTCs: B1200, B1269 and B1271.

    With the hot weather being a factor and the flooded tyre well of a few months ago, the Battery Blower looked like the best place to start. However, along with the other DTCs there could be a common cause which someone far more knowledgeable than me, might be able to point me towards? I look forward to hearing from him or her.
     
  9. ChapmanF

    ChapmanF Senior Member

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    The wiring diagram shows that the motor is speed-controlled via the low side. The motor's high side always has +12 volts (well, whenever the relay is energized), and its "GND" side is really wired to the motor controller, and won't be pulled down to actual body-ground voltage unless the highest speed is selected. At intermediate speeds it will be pulled down by intermediate amounts, and if the controller isn't being commanded to run at all, it will be up near battery voltage (so, zero volts across the motor).

    People do seem to commonly assume that when the VSC/brake/ABS lights are on, the car must be talking about the brakes, and then if the brakes seem ok, it must not be talking about much, and so continue using it.

    Something that maybe hasn't been publicized as much as it should be is that the brake ECU gets notified of problems elsewhere in the car. If there is a problem detected with the traction battery or hybrid powertrain, the brake ECU is notified so it will know it can't count on regen and will have to handle braking on its own. Those notifications will light the brake warnings on the dash, but that doesn't mean the car is just talking about some brake issue that can be dismissed by saying the brakes seem ok.

    In this case, because you had the red triangle also, you know there was a problem elsewhere in the car, and the brake warning lights were likely just secondary to that.

    The P0A84 definitely refers to the battery blower, saying its measured voltage (from the "GND" side of the motor, which as discussed above isn't literally at ground all the time) was lower than it should be. P3000 is just the HV ECU saying it's aware of a code from the battery ECU, which would be your P0A84. B1421 only means there wasn't strong sunlight on the dash when you pulled the codes.

    C2310 and C2318 both refer to low supply voltage observed at the Transmission Control ECU (grandiose name for the circuit that moves the transmission in and out of Park). It gets supply voltage at a couple different terminals, one all the time (to retain its memory and such) and one only when the car is IG ON. C2310 means it saw something less than 10 volts at its always-supplied terminal, and C2318 that it saw something less than 9.3 at its IG-switched terminal. These codes don't always mean a problem with the 12 volt battery, as these voltages are measured at the transmission control ECU so they can also be affected by wiring or connector issues on the way there. But it wouldn't be unreasonable to pause here and check your 12 volt battery health and give it a good full charge if need be.

    Any of these codes that show with 'snowflake' icons next to them in Techstream will have "freeze frame" data collected at the moment the code was set. You can click those icons in Techstream and get more details like exactly what voltage was being seen by the Transmission Control ECU at the moment it set each of those codes, and what it was trying to do at the time. That information might be worth posting here.
     
  10. harryarcos

    harryarcos Junior Member

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    Many thanks for your help and such a detailed reply. I will charge up the battery and put it all back together, because everything that I have tested so far seems OK. If possible, I would like to test the actual blower motor controller before putting it all back. It looks very similar to the one for the cabin blower in my Saab and that had a semiconductor which failed and I was able to replace. It was more accessible than that in the Prius. If anyone has the info. on how to test it, please let me know.

    My Techstream is a very early version, so not sure if it has the option of freeze frame data, but if it has, I will post it.
     
  11. ChapmanF

    ChapmanF Senior Member

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    I don't think I know offhand any better ways to test it than what's in the repair manual.
     
  12. TMR-JWAP

    TMR-JWAP Senior Member

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    if I remember correctly, the HV battery fan controller is identical to the one used for the cabin fan. Not 100% sure on this, tho.
     
  13. harryarcos

    harryarcos Junior Member

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    Good chance that they are much the same. I now recall that when the Saab one failed, the cabin motor went to high speed and could not be altered. For anyone new to this, the blower motor controller is just a semiconductor attached to a heat sink (it is shown as a transistor on the HB-45 drawing, but the correct name for it escapes me). It is positioned in the air duct to help cool it. Variable voltage is applied to one leg of the 'transistor', which alters the resistance between the other two legs controlling the voltage and thus fan speed. At the lower settings, I would guess that it becomes pretty hot.

    Easy enough to test on the cabin fan, but the battery blower motor only works when needed to cool the HV battery, so I will have to wait for another hot day as the weather has turned back to the usual very mild with rain here in the UK.
     
  14. harryarcos

    harryarcos Junior Member

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    I only have the Haynes manual, which is not a lot use, so was pleased to find the HB-45 extract on here to get me started. Although the section gives a test for the connections, there is nothing about testing the actual controller, which should be simple enough with a multimeter. If the better repair manual has the info. I would be grateful if you could post it.
     
  15. TMR-JWAP

    TMR-JWAP Senior Member

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    Most apps like Hybrid Assistant have the ability to run the HV Battery fan through each of it's speeds, step by step.
    I know for fact that my HA app can do all 6 speeds individually.
     
  16. ChapmanF

    ChapmanF Senior Member

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    It would become crazy hot if it were actually used that way, as at intermediate voltages it would be dissipating large amounts of power.

    Instead, the ECU sends it a train of pulses. It is either off, dissipating no power, or fully on, dissipating the minimum power it can in saturation. The ECU varies the motor speed by changing the width of the pulses, which changes the average voltage seen by the motor, but without ever really using the transistor as a variable resistance.
     
  17. harryarcos

    harryarcos Junior Member

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    Thanks. That sounds like just what I need, although presently not having the necessary Bluetooth OBD connection. I might also need an Android device, unless the workaround on tarkitheme.com works.
     
  18. dolj

    dolj Senior Member

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    It is one of the active tests in Techstream too, seeing as you mentioned you have it.
     
  19. harryarcos

    harryarcos Junior Member

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    I bow to the superior knowledge.

    I am still hoping someone will come up with what the resistance readings should be between the 4 terminals marked GRD, SI, +B and VM so I might either confirm or eliminate that it is faulty. Thinking back, I can only remember once hearing the blower fan running at a high speed. If it ran at lower speeds, then I did not hear it.
     
  20. ChapmanF

    ChapmanF Senior Member

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    It's really no use thinking of it that way, because it's not a resistance device.

    Checking it in action as shown on HB-161 and HB-162 is the ticket. (However, I think there may be a typo in the definition of "A" in step 18. The basic idea here is that with speed 1 selected, the motor should be seeing 2 to 4 volts. The high side of the motor is always at battery voltage, 12 to 14ish, and that would put the motor's low side 8 to 12 volts above ground. Looking at the diagram, that should be the same voltage you see from the controller's VM to body ground, assuming your meter is slow-responding enough to show you average voltage and not the pulses. The relationship where that voltage is A−2 to A−4 would hold if A were your measurement from the motor's high side to ground. At least, that's the way I'm reading it.)
     
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