Hybrid battery problem or just its cooling fan?

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by Tipjar, Apr 10, 2026 at 5:11 PM.

  1. Tipjar

    Tipjar Junior Member

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    IV
    My wife's 2015 Prius C with only 60,000 original miles has been showing the "Check hybrid system stop the vehicle in a safe place immediately" warning message off and on for the past two years. It always happened on particularly hot days which makes sense because the temp sensors around the hybrid battery trigger the dash warning. We learned to keep the intake and exhaust vents for the battery unobstructed. The hybrid battery's cooling fan has always been clean, I've even completely dismantled it to be sure, and it didn't need taking because part there was dirt or debris inside it. The warning message won't appear if I happen to have the access panel to the regular battery off (which is right next to the hybrid battery). Presumably because the battery is getting all the cooling it needs.

    Now I'm running down my options. I've seen the hybrid battery's cooling fan working at a low speed on occasion. Is it possible for the fan to be bad but still operate at a low speed? Can I check the health of the hybrid battery's cells with an obd reader and Dr. Prius software or does it really require a shop with better equipment to determine if one or more cells are bad?
     
    #1 Tipjar, Apr 10, 2026 at 5:11 PM
  2. BiomedO1

    BiomedO1 Senior Member

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    You need to first get us the trouble codes it's throwing; because it's obviously intermittent. The trouble codes will tell you what the ECU doesn't like, because right now your just guessing. The OEM clearly states to keep those vents clear, just because your doing that now, doesn't mean that you haven't already damaged the traction pack. This is like, not doing an oil change until the oil lamp lights up. Is the AC working and do you use it? Set the HVAC to auto and 70 degrees to see if the problem reoccurs.
     
    #2 BiomedO1, Apr 10, 2026 at 5:26 PM
  3. Tipjar

    Tipjar Junior Member

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    #3 Tipjar, Apr 10, 2026 at 6:24 PM
  4. JamesSmith66

    JamesSmith66 New Member

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    Dr. Prius is more than enough to catch the specific error code. Once you pull that data through the scanner, it'll be pretty obvious what's actually triggering the warning.
     
    #4 JamesSmith66, Apr 10, 2026 at 6:31 PM
  5. bisco

    bisco cookie crumbler

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    a prius aware scanner should give you more detailed codes. look into autel maxi 200. idk if it will work with the c or not.
    dr prius will give you module voltages. it might be worth opening up the battery and looking for corrosion
     
    #5 bisco, Apr 10, 2026 at 7:51 PM
    Tipjar likes this.
  6. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    A good scanner is the right start to troubleshooting.

    It's easy to say that a 2015 should be due for replacement about now; that's a pretty normal expectation. But maybe not. A report from a good prius-aware scanner should help.

    Good luck!
     
    #6 Leadfoot J. McCoalroller, Apr 10, 2026 at 9:32 PM
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