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Help diagnosing some code: C1241, C1271-78, +more

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by jds580s, Jul 16, 2016.

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  1. jds580s

    jds580s Junior Member

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    Vehicle:
    2021 Prius Prime
    Model:
    Limited
    My 2007 Prius hasn't been giving me any problems other than one tire pressure sensor thinks a tire is low even when it's not.

    Today I received the yellow (!) warning on the dash.

    I took it into my auto parts store to read the codes and they found a whole lost of them.
    1. C1241 - too low or too high battery volts
    2. C1271 - Low Output Voltage of Right Front Speed Sensor
    3. C1272 - Low Output Voltage of Left Front Speed Sensor
    4. C1273 - Low Output Voltage of Right Rear Speed Sensor
    5. C1274 - Low Output Voltage of Left Rear Speed Sensor
    6. C1275 - Abnormal Change in Input Voltage of Right Front Speed Sensor
    7. C1276 - Abnormal Change in Input Voltage of Left Front Speed Sensor
    8. C1277 - Abnormal Change in Input Voltage of Right Rear Speed Sensor
    9. C1278 - Abnormal Change in Input Voltage of Left Rear Speed Sensor
    10. C1281 - Master cylinder (M/C) pressure sensor output signals is faulty
    11. C1346 - stroke sensor zero point learning abnormality
    12. C1378 - Capacitor Communication Malfunction
    They didn't know much more than that.

    I've seen odd codes come up before and it ended up being my 12v battery so that was the first thing I checked. I tested it under no load, on ACC and while charging and it's all in spec. I last changed it 14 months ago and it's still under warranty so I was kind of disappointed it wasn't going to be that easy.

    Car has been and stil is running well.
    The only recent things to mention
    1. We had the oil changed and the tires rotated 2 days ago.
    2. Today my wife accidentally pushed the park button (while moving). The car went into neutral and she lost ability to accelerate until she shifted out of neutral.

    So I'm stuck between wondering if any damage was done when shifting into park, or if something was with the brakes was effected during the rotation.


    Any good guesses or things I can check to start ruling out possibilities?

    Thanks!!
     
    #1 jds580s, Jul 16, 2016
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Pushing the P button while in motion would not cause damage to the car.

    If you want to DIY you will need a digital multimeter so that you can measure voltage and resistance. With so many fault codes logged by the skid control ECU, the problem is one of the following:

    1. Weak 12V battery (which I realize you've tentatively ruled out)
    2. Failed brake power supply (this is the black rectangular unit next to the 12V battery)
    3. Bad wiring harness between the brake power supply and the skid control ECU
    4. Failed skid control ECU (near steering column)

    If you obtain the factory repair manual info at techinfo.toyota.com, you can follow the troubleshooting tree for DTC C1378 and see where it leads you. You may need access to an oscilloscope if some of the simpler troubleshooting tasks do not point to a failed component.
     
    #2 Patrick Wong, Jul 16, 2016
    Last edited: Jul 16, 2016
  3. bisco

    bisco cookie crumbler

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    Plug-in Base
    how many miles on her? is it possible to over tighten the lugs enough to damage the wheel bearing/speed sensor?
     
    #3 bisco, Jul 16, 2016
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I would not think that to be possible. Since all four wheels are reporting a problem, I would say it is more likely to result from a common cause such as insufficient 12V power or a failed skid control ECU. C1241 also hints at low 12V power.
     
    #4 Patrick Wong, Jul 16, 2016
    bisco likes this.
  5. jds580s

    jds580s Junior Member

    Joined:
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    Vehicle:
    2021 Prius Prime
    Model:
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    I'll share some follow-up for anyone else searching about these codes.

    Shortly after the original post the break warning light on the dash turned off. I tested the 12v battery more and it still looked good according to my readings and in the diagnostic display on the MFD.

    It did come on again the next day but only for one short trip and stayed off after that.

    I hadn't heard about the brake actuator assembly warranty enhancement, but my notice came in the mail the day after this happened.
    I figured this issue was going to be beyond what I would be able to diagnose and decided to take it into Toyota.
    Go figure, they said the codes were related to the brake actuator and would be replaced under the extended warranty.
    My 2007 slipped in just before the 10 year/150k mile cutoff

    They had to order in the part and should have it ready for me later today.

    Thank you both for the recommendations!
     
    #5 jds580s, Jul 27, 2016
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