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Help Diagnosing Persistent BRAKE, ABS, VCS, and ((!)) Lights

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by gdowdy3, Oct 8, 2023.

  1. gdowdy3

    gdowdy3 New Member

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    I've had my 2007 Toyota Prius for ~5 years now, and it has given me rather little trouble. However, I've now got an issue that I need help diagnosing.

    First, here's the relevant history...
    1. My car was functioning just fine, with no warning lights.
    2. I went on vacation for about 10 days, during which time my car was idle, sitting in the driveway.
    3. I returned from vacation, and I drove the car to a local restaurant, not noticing any warning lights.
    4. Leaving the restaurant, I returned to my car, and turned it on following the usual procedure. I immediately noticed that the BRAKE, ABS, VCS, and ((!)) lights were illuminated, with the BRAKE light glowing red, and the others glowing yellow/orange.
    5. I drove the car home (slowly and carefully) on local roads (i.e., no highways).
    6. I started the car again the following morning, and the lights were still present.
    7. After googling the issue, I concluded that the explanation might just be a weak 12V battery, which seemed plausible given that the car had sat idle for 10 days, and that the battery was at least 5 years old.
    8. I measured the voltage across the terminals of my "12V" battery with a voltmeter. Multiple measurements gave anywhere from 11.8 V to 12.2 V.
    9. I also noted that the voltage measured by the car itself in the diagnostics screen was 11.4 V.
    10. These measurements led me to conclude that the battery's performance was borderline at best, and that I needed to replace the battery to rule it out as the cause of the warning lights.
    11. I removed the old battery, bought a new one (same part number) from my local Toyota dealer, and then installed the new battery myself.
    12. I measured the voltage with my voltmeter: 12.8 V. I also measured it using the car's diagnostics: 14.8 V.
    13. I again started the car, hoping that the warning lights would not reappear. Unfortunately, they did.
    14. I've ordered an OBDII port reader online. It's supposed to arrive tomorrow.
    15. Reading other threads on PriusChat, I learned how to get the "blink codes" from the car using the janky paper clip in the ODBII port trick. I got one code from the ABS light, one from the VCS light, and one from the ((!)) light. The codes are as follows:
      1. ABS: 42
      2. VCS: 45
      3. ((!)): 64
    Based on what I've read on other threads, my understanding is that the 42 and 45 codes are general warning messages that don't give me much information. However, the 64 code corresponds to DTC C1343, indicating a "Rear Hydraulic System RH Malfunction".

    I have requested a copy of the Repair Manual from my local library, but it will be a few days before it arrives. So, in the meantime, I wanted to ask this community for guidance. In particular, I'm interested in opinions on the following:
    1. Is it plausible that there's really nothing wrong with my rear hydraulic system, and that DTC C1343 was raised simply because of low battery voltage?
    2. If the theory above is correct, since I've already replaced the battery, that should fix the root cause. Accordingly, if I somehow clear the DTC codes, they shouldn't return. On the other hand, if the above theory is incorrect, then I almost certainly haven't fixed anything, and clearing the DTC codes should make them go away only temporarily. Bottom line: it seems that I have nothing to lose by doing a test where I clear the DTC codes and see what happens. Any thoughts to the contrary?
    3. Where is everyone getting their Toyota Techstream tools from? When I search for this product on Amazon, I see a large number of vendors, most of which look rather sketchy. For example, most warn that I'll have to disable anti-virus software to use the device, which makes me uncomfortable. Are there any Toyota Techstream tools which don't require disabling anti-virus software?

     
  2. Brian1954

    Brian1954 Active Member

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    Which one did you order? Most of them are not capable of reading all the trouble codes in a Prius because they can not communicate with all the ECU's in the car.

    Posted via the PriusChat mobile app.
     
  3. Tombukt2

    Tombukt2 Senior Member

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    Yes it's very possible that the low voltage scenario of your 12 volt could cause computers and general gateway failures if you will and no com issues.. You don't want to be believing anything and start a bunch of troubleshooting procedures until you know you have a solid 12 volt power supply that does not waver just sitting there running the car not necessarily with all the lights on but at least the car up and ready sitting air conditioner off climate control off just sitting there You need to have a solid stable 12 volt power supply If you don't you may be walking around and around yourself for days trying to grasp straws that aren't even there believe it.
     
  4. gdowdy3

    gdowdy3 New Member

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    I ordered this one, because it claims to have the ability to read and clear codes associated with ABS: "ANCEL AD610 Plus ABS Airbag Bidirectional Test OBD2 Scanner Diagnostic Tool, with ABS Auto Bleed SAS Calibration Oil Light SRS EPB Reset Engine Code Reader". You can find the exact product by searching for this string on Amazon. (Looks like this forum doesn't allow me to post the link.) If it turns out that the tool doesn't meet my needs, I'll return it.

    I would happily order one packaged with Toyota Techstream if I could find one that doesn't require me to disable anti-virus software on my computer. (See question #3 in my original post.) Any recommendations?
     
  5. ChapmanF

    ChapmanF Senior Member

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    The 42 and 45 have rather more specific meanings than that. You can read about them on this PriusChat wiki page:

    Blink (a/k/a Flash) Codes – How to. | PriusChat

    The ABS function saying 42 means it is aware of a code from the ECB function—((!))—and is telling you to look at that. The VSC function saying 45 means the same thing: it also is aware there's an ECB code, and telling you to look there.

    The ECB 64 is indeed C1343, and means the brake ECU had trouble applying and holding the amount of fluid pressure it wanted at the right rear brake. That can be for a few possible reasons; there are five different INF codes for C1343, but you can't get the INF codes with light blinks. A scan tool is needed for those. Causes could include a leak, a worn or sticking valve in the actuator, a need for air bleeding, even just a wobbly rotor (which makes the fluid pressure fluctuate, so the ECU feels like it's lost its ability to hold a steady pressure).

    All sources for Techstream other than Toyota are going to be sketchy one way or another. They've all taken Toyota's tool and broken it somehow to make it not check your subscription, and the kinds of tricks they have to use to accomplish that are pretty much the kinds of tricks anti-virus software is built to catch.
     
  6. gdowdy3

    gdowdy3 New Member

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    Thanks for weighing in, ChapmanF!

    You said:

    Since you did not list a failing battery as one of the possible causes, can I assume you are confident that this is not the cause?

    Also, you said:

    Is it possible for an average citizen and non-mechanic like myself to purchase Techstream from Toyota?
     
  7. gdowdy3

    gdowdy3 New Member

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    PXL_20231010_013056974.jpg

    Update: My OBDII port reader arrived in the mail. I used it to confirm the presence of DTC C1343. I then used the tool to clear the code. However, I found that it reappeared as soon as I depressed the brake pedal. So it appears that the battery was not the problem. :\

    Now I guess I'm left waiting on the arrival of the Repair Manual at the local library. In the meantime, is there anyone out there with a copy of the Repair Manual kind enough to tell me what it says regarding DTC C1343?
     
  8. ChapmanF

    ChapmanF Senior Member

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    Pretty confident, yes. You'll find frequent advice in the manual to quickly check the voltage isn't below 11 and charge or replace if necessary before proceeding with diagnosis, and you didn't report any voltages that low. Also, you don't have C1241, which is the code the brake ECU sets when it's telling you "hey, voltage kinda low here." Several of the ECUs in the car are programmed to watch the voltage and set such codes. They're usually programmed to set at around 9.5 V or so, which is definitely low for the car but still well above what the microprocessors need to function; it's not like they're on their last gasp when they do their job setting those codes.

    There's always been a kind of popular belief you can go change the voltage at some decimal place after the 12 and turn the car's ECUs into random code generators, but they really just don't work that way.

    Anybody who wants to can get it, but 'get' ≠ 'purchase'. The way Toyota provides it is as a download, which doesn't work until you feed it a subscription to Toyota's Technical Information Service (TIS, the web site). You can keep the download around on your computer as long as you want, it just only works when your subscription is paid up. A working shop might go for the year-long subscription ($1360) but most average citizens and non-mechanics will opt for the two-days-at-a-time version ($70).

    Two tips: one, if you start your subscription on a Friday, you can get more than just two days out of it. Two, don't wait too late in the day Friday to start it. Their online payment system is famously clunky and sometimes your payment goes through and you wait the ten minutes or even an hour and try to sign in and still can't. Their tech-support people will respond and fix it and even extend your time—but you gotta call within their tech-support hours. Once the do whatever they do and make the payment go through, you're good; it's not going to flake out in the middle of the weekend or anything.

    If you get it that way, it's still on you to supply the computer, and the dongle for connecting the computer to the car. There is a specific dongle Toyota recommends—they use it in their testing and their tech support will help you with it in case of problems—but it's around $500. (Just a one-time purchase though; whatever dongle you choose, you buy it outright.) Theoretically, any dongle that supports "the J2534 standard" should work. You can find a bunch of threads around here on different choices of dongle that cost less than Toyota's favorite, and how well they work.
     
  9. SFO

    SFO Senior Member

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    Welcome to PriusChat!!
    Here is the workup for DTC C1343 (and C1341 C1342 C1344) : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/21avn/cic13416.pdf
    There is a preinstalled version of techstream, then you shouldn't have to worry about turning off your AV software.

    FYI : you're moderated until you've posted 5 times.
     
  10. gdowdy3

    gdowdy3 New Member

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    Thanks for your help, ChapmanF and SFO! I've got another interesting observation to report...

    My Ancel OBDII port reader allows me to see live sensor measurements. In particular, I can see the live measurements of four sensors titled "FR Wheel Cylinder", "FL Wheel Cylinder", "RR Wheel Cylinder", and "RL Wheel Cylinder". When I just sit the car without my foot on the brake pedal, these four sensors read as follows:

    No brake.jpg

    When I step down on the brake pedal, the values associated with FR, FL, and RL increase. However, the "RR Wheel Cylinder" measurement remains the same:

    With brake.jpg

    To me, this suggests that one of the following two scenarios is true:
    1. The hydraulic fluid routed to the right rear wheel is not being appropriately pressurized when I step on the brake pedal, or
    2. The hydraulic fluid routed to the right rear wheel is being pressured just fine, but the sensor is not measuring the pressure correctly.
    Do you agree with this conclusion? Are there any other scenarios you can think of that might explain my observations?

    To try to distinguish between the above two scenarios, my next step is to try the following experiment:
    1. Elevate the right rear wheel with the jack.
    2. Remove the parking brake.
    3. Confirm that the right wheel spins freely (by hand).
    4. Depress the brake pedal.
    5. Check if the righ wheel spins freely.
    If the right wheel spins freely, that suggests that Scenario 1 is true.
    On the other hand, if the wheel does not spin, that suggests Scenario 2 is true.

    Please let me know if you have other ideas!
     
  11. gdowdy3

    gdowdy3 New Member

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    While waiting for my wife to return to help me with the experiment described above, I've made another interesting observation...

    My Ancel device also gives me live measurements of the currents through the solenoids responsible for controlling the brake hydraulics. When I'm sitting in my car, with my foot off the brake pedal, the SLARR, SLARL, SLRRR, and SLRRL currents all read as 0 A.

    No brake current.jpg

    However, when I step on the brake pedal, the SLARL and SLRRL currents both jump up, while other two stay at 0 A.

    Brake current.jpg

    The SLARL current is fleeting; it quickly goes back to 0 A, even while my foot is still on the brake. The SLRRL current remains elevated until I remove my foot from the brake.

    I've included this observation just for completeness. However, the main point is that the SLARR and SLRRR currents (both corresponding to the RR wheel) do not respond to me stepping on the brake pedal. I believe this is consistent with Scenario 1 in my previous post. If the solenoids that are supposed to pressurize the RR wheel cylinder are not active, it makes sense that the pressure in the RR wheel cylinder remains flat.

    So, now the question is: why are those solenoids inactive? If anyone has any theories, please feel free to share!
     
  12. gdowdy3

    gdowdy3 New Member

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    An unexpected plot twist...

    Reading the repair manual, I came across the following: "The voltage between the terminals of the brake actuator assembly may become 0 V due to the fail-safe function when the ECB warning light comes on (malfunctioning)."

    This got me wondering if the lack of current in SLARR was, in fact, due to the fail-safe function, induced by DTC C1343 being raised. To test this theory, I cleared the code, and then again tried to measure the SLARR current when I stepped on the brake. Sure enough, I could see current.

    I thoroughly expected my stepping on the brake to cause DTC C1343 to be raised again. But it didn't. I stepped on the brake several more times (with varying levels of force) to see if I could get DTC C1343 to appear again. It didn't. Furthermore, I am now able to see the reading associated with the pressure in the RR wheel cylinder increase when I step on the brake.

    I even restarted the car and tried again to get DTC C1343 to resurface by stepping on the brakes. Nope.

    So I'm thoroughly confused. It seems very unlikely that I fixed the problem with my experimental poking and prodding today (looking inside the brake drum, disconnecting and reconnecting the brake control power supply, and so on). Yet, I can't get DTC C1343 to reappear. So I guess I'll just keep my fingers crossed that the code doesn't reappear. But, if it does, I'll investigate further.
     
  13. mr_guy_mann

    mr_guy_mann Senior Member

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    Well, if it works then it works. I might look at the pressure sensor voltages for both rear brakes and see if they are the same left to right with different amounts of force applied to the brake pedal.

    Also try to see if both rears increase at the same time. (the update speed on the scantool might not be quick enough to make this test useable).

    If there is air or some other fault in the right rear hydraulic circuit, then pressure would take longer to increase by the same amount as the left side (assuming it could ever reach the same pressure at all).

    Posted via the PriusChat mobile app.
     
  14. gdowdy3

    gdowdy3 New Member

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    Thanks for weighing in, mr_guy_mann!

    Your suggestion is timely, because, just yesterday, I drove my prius around the block, periodically stomping on the brakes to (a) ensure that they worked and (b) see if I could get the dash lights to come on again. Sure enough, the third or so time that I stomped, the warning lights came back on.

    I'm going out to the car now to confirm that it's still DTC C1343. Assuming it is, I'll see if I can generate time plots of the pressure sensor voltages... Stand by...
     
  15. gdowdy3

    gdowdy3 New Member

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    Confirmed: DTC C1343 has returned.

    As before, it seems that the presence of DTC C1343 prevents solenoid SLARR from activating, because I can't measure any current through that solenoid, nor can I affect the pressure in the RR cylinder (by stomping on the brake) until I clear that code.

    However, once I cleared the code, I was again able to measure current through the solenoid and varying cylinder pressure when I stomped on the brake pedal. Here are some plots showing the results. It does seem that the pressure in the RR cylinder tends to be a little bit slower to rise than the pressure in the RL cylinder.

    Does that look like the sort of delay you'd expect if there was an air bubble in the RR hydraulic line? Should I try to bleed the line?

    PXL_20231018_005523547.jpg PXL_20231018_005530564.jpg PXL_20231018_005537808.jpg PXL_20231018_010140896.jpg PXL_20231018_005739532.jpg PXL_20231018_005848756.jpg
     
  16. mr_guy_mann

    mr_guy_mann Senior Member

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    Yes, I would follow the brake bleed procedure in the service manual - I assume that there are no external leaks in the hydraulic system. When you lift the back of the car to reach the bleeders, might want to pull the drums and inspect things. Make sure the shoe adjustment is "close".

    Posted via the PriusChat mobile app.
     
  17. gdowdy3

    gdowdy3 New Member

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    So I obtained a copy of the "Haynes Repair Manual" from my local library, but it says basically nothing about how to bleed the brake hydraulic lines. So I followed the procedure shown here:
    .

    In so doing, I drained my brake fluid reservoir from MAX to about halfway between the MAX and MIN line.

    I also removed the brake drum on the RR wheel so I could look at the insides. Nothing was clearly amiss to my untrained eye (see images below). I turned the "star wheel adjuster" to ensure that the brake shoes were close to the drum but not dragging.

    Unfortunately, this did not resolve the issue. DTC C1343 returned shortly after I started up the car and pumped the brakes a few times. Also, as you can see in the attached time series plot, the lag between the RR cylinder pressure and the RL cylinder pressure seems like it might even be more pronounced than before.

    Anyone have any advice?

    upload_2023-10-22_17-5-19.png

    upload_2023-10-22_17-6-12.png
    upload_2023-10-22_17-6-29.png
    upload_2023-10-22_17-6-55.png
    Cylinder Pressure TS.jpg