C1241, C1256 help please

Discussion in 'Gen 2 Prius Main Forum' started by Figster10, Mar 2, 2019.

  1. Figster10

    Figster10 Member

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    so, just bought this car and it drove fine no issues but of course this is happening. I will check the 12v battery again later but can anyone help me in figuring out how to diagnose this. I know the snowflake sends me to view all the different relative measurements but what exactly am I looking for? I can do any repair no problem I’m just wondering where I need to begin. Thanks and God bless
    John 3:16
    Acts 2:38
     
  2. Figster10

    Figster10 Member

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    Codes in pic
     

    Attached Files:

  3. Raytheeagle

    Raytheeagle Senior Member

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    When you click on the snowflake, then next screen it sends you too will have a more specific INF code that can be researched for additional details.

    Anything happen that may have caused the codes to appear?
     
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  4. Figster10

    Figster10 Member

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    The car was bought at an auction and sometimes the 12v batteries get drained being left on overnight or whatever. That’s why I will go back and test battery before and after start.

    2008 Prius no accidents with 233k drove for 50 miles back to office no crazy issues. “Brake, ABS, exclamation point logo” light on with no red triangle.
    There are two things to note though: humming noise here and there from firewall inverter area that goes 5 seconds in and out during idle. Also, it sounds like rear wheel bearing is going out. I hear it going 65 mph only.
     
  5. dolj

    dolj Senior Member

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    It looks like the brake accumulator is not happy.

    What is your skill level in regards to doing your own repairs?
     
  6. Figster10

    Figster10 Member

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    My skill level is advanced. I have changed fuel pumps, brake boosters, opened these hybrid batteries, opened valve covers and changed suspensions on my own. I would imagine replacing this costly accumulator is very similar to replacing a brake booster on any other car, right? I have opened and taken apart a power inverter on my prius before almost think I know how to get to the accumulator before slowly taking it apart. I am hearing there's a "prius" way to finish this repair using techstream(which I have and know how to use) but not quite sure if there's anything I need to know before taking this project on starting tonight. Thanks and God bless
     
  7. dolj

    dolj Senior Member

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    That is good then. The C1241(Low Battery Positive Voltage) is secondary at this point, just make sure your 12 V aux battery is charged up full (12 .7 V +) and keep it on a maintenance charger while you work on the C1256 (Accumulator Low Pressure).

    Here is the Inspection Procedure for DTC C1256

    Good luck and keep us updated on how it goes.
     
  8. ChapmanF

    ChapmanF Senior Member

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    Be careful not to assume too quickly that a C1241 code from the skid ECU (with the word "voltage" in its fortune cookie) is telling you anything about your aux battery. It is based on a voltage measurement at the skid ECU. There's a one-way implication: if you know your aux battery voltage is dreadfully low, then you might reasonably assume the C1241 is because of that, until you have the battery charged. But otherwise, the code is telling you to investigate why the voltage reaching the ECU is low, and the possible reasons for that are numerous.
     
  9. Figster10

    Figster10 Member

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    So, I followed the inspection document you sent me and did the voltage check to the wheel pressure sensors and acc sensor 1. I saw no crazy drops from outside the range the document you sent has. I did however reset the aux battery to clear codes and the lights came back on right away which automatically has me thinking it’s a hard code situation aka possible electrical issue. The inspection document states if numbers are in range then skid Ecu needs replacement. Without testing the electrical checkpoints on actual accumulator can I really assume it’s the ecu and is that enough to cause that washing/winding noise on my firewall?
     
  10. Figster10

    Figster10 Member

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    12v six battery measures

    Cold with car off: 11.4-11.7

    With car on: 13.7-ish
     
  11. Figster10

    Figster10 Member

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    Aux, not six
     
  12. Skibob

    Skibob Senior Member

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    That’s pretty low
     
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  13. Figster10

    Figster10 Member

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    Aux battery does seem pretty low but I'm wondering if it's enough to create that sound from the firewall area of my car which can be heard through my ac. I'm down to accumulator-aux battery-ecu skid. Worst case scenario it's the darn accumulator just because I don't have time to swap out part this week.

    Any suggestions on how to rule out one or the other would be greatly appreciated. The self diagnose sheet helped but I may still be stuck at ruling out the ecu skid vs accumulator. Thanks and God bless
     
  14. Skibob

    Skibob Senior Member

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    The only way I can think of is to try to charge the battery and see if it helps. If the voltage is still low your going to need a new battery anyway. I had weird brake problems when my battery was about that low. Have not had a problem since I replaced it. I do remember there was some corrosion on the terminals on the old battery. After I cleaned them the problem also went away. So...try cleaning the terminals and charge the battery? It’s free to try.
     
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  15. Figster10

    Figster10 Member

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    I will do that today and see what happens.
     
  16. Skibob

    Skibob Senior Member

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    Ha, ha. When you are logged on the green dot looks like Moe is skeet shooting. :LOL:
     
  17. dolj

    dolj Senior Member

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    The question is, how much lower is it being dragged down once the car starts firing up all its gadgetry, before the HV relays kick in the HV battery?
     
  18. Figster10

    Figster10 Member

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    So far I have used a multi meter to test three different batteries for the same car. They have all shown similar and good readings but then again the problem is still present. It says 11.7v on the monitor in the car but multimeter says 12.78v. When the car turns on it goes up to 14.7 no dipping whatsoever.

    I didn’t see too crazy dips in the diagnostic of the techstream for the accumulator and wheel pressure sensors.

    I’m left wondering if because after I reset car the lights came back on immediately after start up could it be possible it indeed is an electrical issue thus pointing to the ecu skid? If I were to lean towards the ecu skid I guess my question then is how do I confirm that? If I’m completely off can someone please provide a way to test the accumulator since I guess the battery to based on multi meter reading seems fine
     
  19. dolj

    dolj Senior Member

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    Something is not right there. Usually the difference between those two is only 0.2 - 0.3 V with the MDF reading the lower. So either something nearer the MDF is pulling a bit of a current or maybe the bad connection/electrical fault is in that area.

    It might be time to refer the wiring diagram so you can trace it. You can download the 2006 RM and EWD using a link in this post here. Big ups to MickyMatter who made that happen. Its a large file btw, 135 MB.
    That doesn't make sense either, because essentially the car is saying it thinks the 12 V battery is totally flat.
     
    #19 dolj, Mar 5, 2019
    Last edited: Mar 5, 2019
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  20. Skibob

    Skibob Senior Member

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    Could the capacitor for the braking system be going bad?
     
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