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Yellow Brake Warning Light

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by salguod, Nov 9, 2016.

  1. Paul Schenck

    Paul Schenck Active Member

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    I had this problem on my 2005 occasionally after 299,000. It would always go away when I powered off the the car so I didn't do anything about it. Replaced the engine and transaxle at 397,000 and the problem reoccurred the other day. Could have to do with the throttle control body. Which had been damaged on the new engine and it was the only part I brought over from the old engine.


    iPhone ?
     
  2. salguod

    salguod Member

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    OK, I finally got my Mini VCI and got it working. (Painful process - short summary is that it doesn't work on Windows 10).

    The report shows several DTCs, but only a couple that are current and should be looked at:

    One is something about the AC sensor in the dash and the other is C1377 - "Capacitor Malfunction"

    Any insight as to what that might mean?

    Evidently the capacitors are near the 12v battery in the back and are related to the regen braking. They also evidently rarely fail.
     
  3. salguod

    salguod Member

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    FWIW, here are all the codes present.

    Oh, and the 12v battery was replaced about a year ago, I think.

    We just turned 190K as well.
     

    Attached Files:

  4. salguod

    salguod Member

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    I have a new symptom. When braking while going very slow I get a lot of clicking noises, more than normal. If stopped and I press harder on the brakes I get a series of clicking sounds, same when I release the brakes. I need to pull new codes and see if anything has changed. I may start a new thread on that. There are a lot of brake clicking threads, but I haven't seen one that addresses my specific symptoms.

    SM-T320 ?
     
  5. salguod

    salguod Member

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    OK, for those still following, today we got more codes and issues. Driving home, after a block my wife got the BRAKE, ABS & VSC lights came on and it beeped for 10 secs. She pulled over and called me and I told her to come straight home. It then beeped again and she continued home & exiting the freeway, about 10 miles or so later, the red triangle came on, the red car error light on the display and it began to beep constantly. Se also noted that the brakes were very hard. She pulled into a lot and at that time a red battery appeared on the screen and a message "problem". She shut the car down.

    I came to pick her up and drove it in a short circle around the lot. Only the red triangle and red car on the display were on and it drove fine. We were only 4-5 miles from home, so I decided to try to get it home. No new lights and no odd symptoms on the way home.

    I connected to Techstream and got the same codes as before plus P0A08 and C1241. C1241 indicates low positive battery voltage, and techstream indicated 10.8v on what I think was labeled B1 & B2. I checked across the 12v battery terminals and got 10.8v initially (and briefly) and then only about 8.6v. With the car on (Ready) I get a brief 13v then it reads about 11.3v. All too low. My 12v battery was replaced in Feb. of '14, a bit early for a failure. One cause of P0A08 is inverter failure, I'm wondering if that's the issue here. The fact that the voltage is higher with the car on, however, tells me that the inverter is working. Can this 12v be tested properly by a parts store like any other battery?

    At any rate, it isn't really reliable to drive at this point so I'll probably get it into the dealer or another mechanic and at least have it diagnosed.
     
  6. bisco

    bisco cookie crumbler

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    yes, any parts store should be able to do a load test. you can check the inverter, by looking for movement in the reservoir.
    it sounds like you might have to bite the bullet and replace the hybrid battery.
     
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  7. salguod

    salguod Member

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    Thanks, I'm going to check all the the connections back there and take it out and take ti to a parts store for a check up.

    Any thoughts on why I'm getting higher initial readings from my meter? I'm placing the probes directly on the battery terminals and the meter is set to VDC.
     
  8. bisco

    bisco cookie crumbler

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    the proper way to check it is after the car has been off for several hours. there is a 'surface charge' after the battery has been charging (whether from the inverter/converter or a battery charger, that must wear off, before true voltage is shown).
    i pop my hood in the evening, open it in the morning, and test the voltage at the jump point while the car is stone cold.
     
  9. salguod

    salguod Member

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    I checked the electrical connections around the 12v battery. The plug to the module next to the battery had some corrosion, which I cleaned up. I also checked the tank for the inverter and found that it was low. Significantly below the "low" mark, but not empty. I did not see any movement in the tank, but the level was low enough that it was tough to see. I plan on getting more coolant after dinner - maybe.

    Of course, the dealer is closed and Autozone lists Pentosin Pentofrost A4 the right one for my Prius. Description:

    Pentofrost A4 is a phosphates organic acid technology (phosphates oat); which is categorized as goat (hybrid organic acid technology) in the US market. Pentofrost A4 is suitable for all Asian vehicles using pink antifreeze/coolant. Pentofrost A4 does not contain any silicate, borate, nitrite or amine containing additives since these may harm your Asian vehicle. Do not mix with other coolants (especially silicates coolants), as this may cause gel formation and clog your radiator. Pentofrost A4 is a pre-diluted antifreeze for Asian vehicle applications in water-cooled engines. It contains phosphates and organic salts to protect all materials used in cooling systems for Asian vehicles. Pentofrost A4 is mixable with all phosphates oat’s. Meets ASTM D-3306.​

    Thoughts?
     
  10. salguod

    salguod Member

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    The manual says SLLC or "any similar ethylene glycol based non-silicate, non-amine, non-nitrate and non-borate coolant with hybrid organic acid technology". Sounds the same, but this post has me worried, but that's a 2001.
     
  11. bisco

    bisco cookie crumbler

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    i would wait until monday and get genuine toyota, especially since you're mixing. but that's just me, and others may advise differently. are you checking the reservoir with the car in 'ready'?
     
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  12. salguod

    salguod Member

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    Yes, car was "Ready". Engine wasn't running.

    Waiting will make getting to work a challenge. If I can sort that out, I will. I don't want cause more trouble.

    I'm curious why you said above that you think I may have to replace the hybrid battery? I have no battery related symptoms, it's always in the blue on the dash, no dramatic fluctuations, etc.
     
  13. bisco

    bisco cookie crumbler

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    it's the P0A08, low hybrid battery cell. but it is possible that a bad 12v can cause faulty codes.
     
  14. dolj

    dolj Senior Member

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    Here are my thoughts.
    That pretty much seals the deal, your 12 V battery is in a poor state. You can try putting it on a charger, but my suspicion is that the battery has sat in a state of declined charge for too long and has been damaged irreparably.
    It is early for failure and it is probably a sign of much worse news to follow below. As I said above I believe your battery is toast, even though you consider it new.
    This is not a good sign. It leads me to believe the inverter charging circuit is not performing properly and together with the information above about the current state of your 12 V battery, directs me to the conclusion the charging circuit has failed. Another possible idea, and I have no basis in fact for this, it is just a WAG, is that the inverter (which has a sense wire directly ion the 12 V battery) can see the battery is too low and shuts down the charging circuit. As you have to at least replace the battery, you could test this theory. See also the good advice on further testing in this regard posted by Patrick, in his post below.
    This only ensures your coolant circulation pump is working, which by what you said later, sounds like it is not.
    This is not good, and needs to be rectified ASAP, do not continue to drive the car until you do. Then check for movement, if none, get that rectified ASAP, and only drive for very short distances until the inverter coolant pump has been replaced.
    Heed this warning. If you do decide to use this, do a full drain, flush (with distilled/demineralised water) and refill. Be aware that flushing will leave your resultant mix weaker, if you use pre mix. Buy concentrate and distilled (or demineralised) water and mix your own slightly stronger to compensate for the residual water.

    I went through this exercise and any non-OEM products that I was sure were a replacement, they were no cheaper, and in one case, more expensive, and together with having to do a full drain, flush and refill, I decided to go with Toyota SLLC.

    YMMV.

    Hope this helps.
     
    #34 dolj, Jan 28, 2017
    Last edited: Jan 28, 2017
  15. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Here are my thoughts:

    1. You can use that Pentofrost coolant.
    2. Use a digital multimeter to measure voltage across the 12V battery while the car is IG-OFF.
    3. Make the Prius READY.
    4. See what the voltage reading is now.
    5. If the voltage reading improves, but is still substantially below 13.8VDC, disconnect the 12V battery negative cable where it bolts to the body, while the Prius remains READY. There will be some sparking when you do that.
    6. Measure the voltage from the 12V positive terminal to body ground. If it is now 13.8VDC, then the DC/DC converter is fine and your problem is a dead 12V battery. Replace the battery in that case.
     
  16. dolj

    dolj Senior Member

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    P0A08 = DC/DC Converter Status Circuit, and is different to the P0A80, that you're thinking of.
     
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  17. bisco

    bisco cookie crumbler

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    thanks. now on top of all my other issues, i'm dyslexic.:oops:
     
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  18. salguod

    salguod Member

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    I think you're right, but I may wait until Monday to get the SLLC just to be sure.
    Done. I get a reading of about 10.8v briefly, then it drops to 8-9v.
    Done. Again, I get a brief 13.something volts then it drops to show about 11.3v.
    I'm getting an improvement, but I'm not sure it's what it should be. I'm confused about why I'm getting the instant higher reading followed by a lower one.

    I'll try your measurement to ground next.
     
  19. dolj

    dolj Senior Member

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    It should be in the range 13.2 - 14.4 V. 13.2 for a fully charge in top condition AGM; and 14.4 for a totally discharged, but otherwise good condition AGM battery.
     
  20. salguod

    salguod Member

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    I'm pretty sure the battery is toast, I now can't get into the trunk.:mad:

    It's almost 10PM here, this now sounds like a tomorrow problem. Goodnight.