2013 US: Check Hybrid System message after heavy rain

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Sandblast7070, May 25, 2026 at 1:04 AM.

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  1. Sandblast7070

    Sandblast7070 New Member

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    Hello everyone, I am a relatively new Prius owner and I am having some trouble figuring out how to diagnose my problem.

    One way or another, during a recent thunder storm rain seems to have gotten its way underneath of my spare tire, and possibly even inside my hybrid battery. The 12v battery seems dry, and none of the fabric trim seems to be wet. I did have the fabric trunk latch + plastic bucket trim out so the spare tire was visible from the trunk. I am confused though, as my weather stripping seems to be fine. I want to run some water over the closed hatch to see if I can find some sort of leak but as of current I have not identified any problem areas.

    When trying to start the Prius I am presented with the display saying "Check Hybrid System, Stop the vehicle in a safe place". There is a triangle with an exclamation point, the ABS light, the odd yellow light that has the car with the lines and another red light I believe also is on. I can't remember at this time but I will try to update tomorrow.

    I have an OBDII reader that only showed the code C1259. I have seen an app called "Dr. Prius" recommended on these forums, and I am currently researching what adapter I should purchase for that. Recommendations are appreciated on that front.

    I tried a couple YouTube videos that had troubleshooting steps. One of which said to pull the orange safety tab off the HV battery, then unplug the white wire (in the front hood fuse box) for 10 minutes. The other which said to turn on the car, put a paperclip in top pin 4 and bottom pin 5 of the OBD plug, press the break 8 times, wait 5 minutes, turn the car off, unplug the wire, wait 20 minutes, and then power cycle the car 3 times. Neither of these methods worked.

    Is there anything else I should / could do in the meantime to troubleshoot and / or prevent damage? I pulled the fabric cover off the battery and felt water underneath of it on the plastic side, and using my flash light I believe I see water underneath the hybrid battery. Again, I am unsure how this even happened. The rest of the car seems to be dry. I do work on my own cars, although this is my first hybrid so I am a bit fresh.

    Thank you, hoping my Prius pulls through without too much damage
    Sandblast7070

    PS; I took the car to the dealership for a recall last week. Something in 2018 about the battery stalling, would that be related if the problem is not water related?
     
    #1 Sandblast7070, May 25, 2026 at 1:04 AM
  2. ASRDogman

    ASRDogman Senior Member

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    You need a scanner that can read ALL the codes.
    It is possible there is an inverter issue. Or the inverter coolant pump. But you need more
    information, thus, a better code reader.

    The weather seal may look good, but that doesn't mean it is. It's common to leak in and down
    toward the 12v battery. It's not very likely it got to the hybrid battery.
    Have you checked all the fuses?

    It "might" be related to whatever the dealership did.

    Be careful about jumping wire from youtube, you could cause serious damage.
    Fabric on the hybrid battery? Do you mean the "trim" pieces?
    The hybrid battery is encased in a metal box. If you see/feel water, perhaps one of the door seals
    have failed. Or the rubber plugs on the bottom frame is missing.
     
    #2 ASRDogman, May 25, 2026 at 8:12 AM
  3. Brian1954

    Brian1954 Senior Member

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    As already mentioned, you need a scanner that can read all the trouble codes. Look at post #1 and then scroll down to post #37 in this thread, https://priuschat.com/index.php?posts/3246758
    I recommend the Autel maxi AP200. It is a Bluetooth OBD2 dongle that uses an Autel app on your phone or tablet. It costs about $60 on Amazon.

    A thread that is specifically about the Autel AP200 is located here, https://priuschat.com/index.php?posts/3248209
     
    #3 Brian1954, May 25, 2026 at 8:48 AM
  4. CR94

    CR94 Senior Member

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    Rainwater coming off the rear of the roof and the sides of the hatch runs into the gutter-like channels under the sides of the hatch. At the bottom end of that channel, the drainwater is supposed to flow between the taillight assembly and body sheet metal. Unforturnately, the passage behind the taillight tends to become plugged with pollen and other debris dropped by trees---assuming you park near trees. As a result, the water leaks into the interior. When that happens on the right side, the 12-volt battery ends up in a puddle of water. The solution is to remove the taillight and clean out the junk behind it.

    That wouldn't explain water under the large NiH battery, if you really have that. Leakage through the seal where wiring enters the hatch may be a possibility.
     
    #4 CR94, May 25, 2026 at 2:57 PM
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