C1241 with loud warning sound, brake, ABS, VSC and tire pressure lights

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Lauren Everett, May 29, 2025.

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  1. Lauren Everett

    Lauren Everett Junior Member

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    Hello all,

    After replacing the transaxle in January (thanks for all of your advice!) I'm back with a new one. Sigh.

    I was exiting the freeway a few days ago when the brake light, ABS, VSC and tire pressure lights all came on suddenly, along with a loud warning tone. I was still able to brake, but maybe with less power than normal (hard to remember because I was trying not to panic). I pulled over and turned the car off, and when I turned it back on everything was fine. I've probably driven 15 miles since then, avoiding the freeway. No issues yet.

    Brought it to a mechanic and they pulled "C1241 ABS voltage too low or too high intermittent." I just replaced the 12v last December and had it tested at the dealership last month when Meineke flagged it as having low voltage. Dealership said it's fine.

    Ant clues as to what could be happening here and how to proceed? Now I'm worried I'm going to lose brake power on the freeway.
     
    #1 Lauren Everett, May 29, 2025
  2. Tombukt2

    Tombukt2 Senior Member

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    Yes your break actuator is going out it's not your 12 volt that's low it's the voltage is low in the braking system not because of the 12 volt because it's not being distributed by the brake actuator properly through the braking system only it's not really anything to do with your 12 volt battery other battery or any batteries this is perfectly normal on this model you haven't changed the brake actuator yet correct well it's going to be time or not and whatever
     
    #2 Tombukt2, May 29, 2025
  3. ChapmanF

    ChapmanF Senior Member

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    C1241 by itself is not any of the codes that indicate any mechanical failure necessarily happening to the brakes.

    Like the book says, it is a code about voltage reaching the brake units being out of spec. If you have a scan tool that can show you the INF codes, they can pin things down a little further.

    The gen 2 brake ECU is really divided into two ECUs that watch over each other, and have power brought in for them on different terminals. Different C1241 subcodes tell you whether it's the voltage arriving at system 1 or system 2 that is wonky.

    Without any other codes indicating mechanical issues, I would at least start just by taking the code at its word and looking for voltage or wiring / connector issues on the way from the 12 V supply to the brake hardware.

    If your scan tool can show you freeze frames, you can get an idea when the C1241 code was set. Was the car READY then, or was the power coming only from the 12 V battery at the time?

    The ECU doesn't know why the voltage arriving is low. You totally can get a C1241 because of a bad 12 V battery. But you can also get it because of corroded or chewed wiring or connectors and that kind of electrical issue along the power path, and not have a problem with the battery at all.
     
    #3 ChapmanF, May 29, 2025
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