Loss of Regen Braking?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by kevelev, Jun 21, 2019.

  1. kevelev

    kevelev Junior Member

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    2011 Toyota Prius 2 (1.8L)

    So yesterday during normal driving, the I had the three lights come on:
    • ABS
    • BRAKE
    • Traction Control/Slipping
    At that time, I lost the regenerative braking function. I kept driving because the mechanical brakes still worked fine. After a few minutes more of driving, the lights went out, and the car functioned normally with all systems working. Next morning I drove to work and all was well, but on the way home, they came on again, with the same symptoms. I also noticed that when this occurs, you can't use cruise control, and the "Energy Monitor" display shows no arrows for where the power is coming from (there may be more symptoms as well that I haven't noticed yet). Maybe there is a bad sensor that's causing a failure/disabling of these systems? I do want to replace my front brake rotors soon, but that's all mechanical. Any ideas? Bad ABS wheel sensor? Help!
     

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  2. ChapmanF

    ChapmanF Senior Member

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    Hi ,

    It is much easier to help you if you post the diagnostic codes that the car reports for why it turned those warning lights on.

    People often read the codes using an old beater laptop with a USB J2534 dongle and Techstream software, though there are other ways. One way that is very quick if you don't have such a setup is to trigger a code blink-out mode with a short length of wire, and count the blinks, and report those here. You can search up many threads here on how to do that.

    Without the reported problem info from the car, we'd all be guessing.
     
  3. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    In your shoes? I'd take it to dealership, have them check it out, see what the trouble codes are.

    I appreciate that's not directly helpful, but it's a rolling computer.

    Should not cost over $100 for that.

    Maybe should have asked first though: do you have anything constantly plugged into OBD port? That caused similar problems for me, in past.
     
  4. bisco

    bisco cookie crumbler

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    how many miles on her? is the inverter pump working?
     
  5. kevelev

    kevelev Junior Member

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    I'll try to get a blink code.
     
  6. kevelev

    kevelev Junior Member

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    130,000 miles, incerter is working well.
     
  7. kevelev

    kevelev Junior Member

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    I actually did have a bluetooth ODB tool plugged in, but's been in there for about a year, with no issues.
     
  8. kevelev

    kevelev Junior Member

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    This might be a good place to start.
     
  9. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I had a scangauge constantly connected, and it was the apparent source of similar issues, dubbed communication errors by dealership. They saw sporadic loss of signal when connecting with techstream, if they wiggled the connection, and suggested I try disconnecting the SG.

    Did that maybe 4 years back, and had no further problems. Seems like having a constant weight on that connector, maybe tapping it with a knee, can be problematic.

    Not saying for sure, and I'm not sure if you still have something hooked up, but if so: but something to try.
     
  10. ChapmanF

    ChapmanF Senior Member

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    Reading the codes is more important than clearing the codes. (Clearing makes reading them harder.) Got 'em yet?

    My ScanGauge hasn't caused me any such problems, at least not since I bought it for my Gen 1 and it came with the non-Gen-1-compatible cable, and I had them send me the other one.

    I did recently see comm errors resulting from a different OBD thingy that I had built using a cheap J1962 connector whose pins were unplated. It worked fine when I first made it, but after about ten years riding around in the glove box, the unplated pins got (invisibly) oxidized enough that it would cause errors just by being plugged in.

    I rebuilt in on a better J1962 connector whose pins are gold plated and it causes no such problems now.

    In my experience, there was nothing subtle about the effect of plugging the bad connector in. Boom, most of the dash lights including the master warning triangle, "PROBLEM" on the MID, the works. And the lights would all stay until the third drive cycle after removing the wretched thing, unless manually cleared with Techstream, which would show a flurry of Uxxxx comm errors reported by multiple ECUs. (Which is kind of what you would expect, for a comm error.)

    In this case, still could turn out to be something more mundane.
     
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  11. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    My experience was "subtle". With SG plugged in, it would be fine for maybe a week, then out of the blue: Check Hybrid System warning, plus 2 or 3 brake and skid-control related lights, plus a strange return-to-defaults feel to the brake.

    This was getting to be a regular event. Discontinued the plug-in, problem never reoccured, and that was close to 4 years back.

    My guess is there was nothing wrong with the connector, but the steady weight, and maybe something a little defective in the OBD port internal connections, would eventually tip the system, upset something.

    It doesn't hurt to try disconnection (if he in fact still has something constantly plugged in), see if that stops the behaviour.
     
  12. kevelev

    kevelev Junior Member

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    I still haven't found any threads that explain how to actually get the codes. I have found a bunch where you respond with a similar message saying to check other threads on this site though. Do you know how to do it?
     
  13. kevelev

    kevelev Junior Member

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    Maybe this (hopefully the Gen 3 behaves in the same way as the Gen 2)?:
     
  14. ChapmanF

    ChapmanF Senior Member

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    I do, as it happens. :) It just gets kind of exhausting to either keep re-explaining it, or searching up the posts where I've explained it before looking for the ones where I explained it best. Sometimes I end up wondering why I'm doing it and not the person who wants the information.

    Here's one with a diagram, might be handy.

    Here's one where I explained the blinking in more detail. It happened to be for Gen 1, where more ECUs blinked, but the principles haven't changed.

    Here's another.

    Can that get you started?

    None of this is secret knowledge, by the way; I know it because it's covered in the Repair Manual, and there's a PriusChat wiki page on how to hook yourself up with that. (Elektroingenieur wrote the wiki page as a way to repost it less often.)

    You'll want that anyway, as having the codes by themselves isn't super enlightening; the manual is what says what they mean and how to find out what caused them.
     
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  15. kevelev

    kevelev Junior Member

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    Thanks a lot Chapman! So for the 4 lights that I have on here were the codes:
    • ABS: 38 41 (it could be 41 38 if I got it backwards, but I think it's correct).
    • Slip/Traction: 43
    • Brake system warning light (the circular one): 36
    • "BRAKE": this light doesn't blink, so no code.
    So I think now I just need to decipher these codes.
     
  16. ChapmanF

    ChapmanF Senior Member

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    I don't think the order actually matters; it's just a set of codes. It cycles around forever, so it 'starts' with whatever one you wrote down first. (I think the computer actually starts the sequence with the lowest one, but again, it doesn't really matter.) As long as you don't mix up the digits and write down 13 and 84. That doesn't happen often, because it is a longer pause in between pairs, long enough to tell the difference.

    38 (a/k/a C1238) has to do with the signal from the right rear wheel speed sensor.

    41 (a/k/a C1241) is listed a few pages later in the manual (making it hard to find if you look where the other ABS codes are) because it's a code that either the ABS or ECB systems can report. It has to do with low supply voltage reaching the brake circuitry. This doesn't always translate to a 12 volt battery problem; as easily it can mean a loose or corroded connector issue somewhere in the wiring harness, etc. But it doesn't hurt to go confirm the 12 volt battery has a reasonable charge. Perfection's not the standard here; voltage below 9.5 (edit: under load) is what'll set the code,

    43 is a VSC code that just means "hey, there's an ABS code, go look at that."

    36 is an ECB code that just means "hey, there's an ABS code, go look at that."

    So it's your two ABS codes that bear looking into.

    The C1238 has a thirteen-page section of troubleshooting steps in the manual so you can pin down what was causing it. (The thirteen pages cover all four codes that are like this one, for all four wheels. It's just the first few pages that are in common to all, and the last six pages that pertain to the rear wheels.) A multimeter is needed.

    There's a reference to a speed sensor signal check procedure (elsewhere in the manual) to try after you have repaired or replaced something. It involves triggering a test mode, then driving a certain distance a certain speed (a big empty parking lot or empty street is good). The test mode is more sensitive than normal, so you find out if the problem is fixed or not faster than you would find out just by clearing the code and waiting for it to come back.

    The C1241 has seven pages of troubleshooting info. It also has a few different three-digit "INF codes" that give you very specific details about what was detected to set the C1241 code. Sadly, you can't get the INF codes via light blinks. A reader like Techstream will get them for you.

    Techstream can also unpack the "freeze frame" that was taken at the instant the code was set and records all of the sensor readings at that instant. For instance, it will have the voltage measurements at several places in the brake system at that time. That can also be very helpful in working out why the code was set.
     
    #16 ChapmanF, Jun 23, 2019
    Last edited: Jun 23, 2019
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  17. kevelev

    kevelev Junior Member

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    Wow, thanks a lot for all the help! This is amazing!
     
  18. kevelev

    kevelev Junior Member

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    So I was hoping to measure the resistance at the wheel bearing/sensor at the RR wheel, so I removed the connector. However, I couldn't make any good contact with the pins so I ended up tearing open the interior panels to get a reading at the next connector at the inside of the wheel well. I think I was expecting between 1500 and 1700 Ohms, but the reading was climbing and basically read like it was an open circuit. I wanted to check and see if that was bad before replacing what's basically be a good wheel bearing (mechanically). So far, all I checked with the 12 V was at the batter. I got a steady 12.3-12.4 V with the car totally off. I think that's shows that the battery is in good shape. I'm hoping from my findings so far that it just needs a new bearing/abs sensor assembly.
     
  19. ChapmanF

    ChapmanF Senior Member

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    For whatever reason (maybe because it wouldn't be simple), the repair manual doesn't give anything like an OK/NG resistance test for a wheel speed sensor. Instead, it approaches the problem by giving continuity/isolation specs for the wire harnesses (starting with the short stub one at the rear that you exhumed the inside end of, and then from there forward to the brake ECU), and a test that the brake ECU is correctly putting 5.7 to 14 volts on the RR+ side of the circuit. The steps end up at replacing the wheel bearing/sensor as the last resort, if you haven't found the problem anywhere else.
     
  20. kevelev

    kevelev Junior Member

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    Hmm, so I should disconnect the sensor at the wheel, then turn on (start engine), and then measure the voltage there? I wish I did that with the wheel off, but I will check it soon, thanks!
     
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