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Brakes catching erratically, ((!)) ABS and BRAKE lights on but full fluid

Discussion in 'Gen 2 Prius Main Forum' started by nathandavidhall, Jul 15, 2021.

  1. nathandavidhall

    nathandavidhall Junior Member

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    Hey all, my girlfriend's '05 Prius with around 220k miles has the condition listed in the subject. By "catching erratically" I mean there's more travel in the brake pedal until they do finally catch, and then it's a more severe/sudden braking than usual (still working effectively though). Brake fluid level is where it should be. I hadn't noticed any screeching or grinding that usually accompanies pads or rotors wearing out.

    I'm pretty handy with wrenches if I have a youtube video as a guide, I've helped a few times on brake work but not super experienced with it, totally willing to take this on if it's not too complex. Any thoughts on what this could be before taking it to a shop? Thanks!
     
    #1 nathandavidhall, Jul 15, 2021
  2. SFO

    SFO Senior Member

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    Happen to have any OBD2 codes (DTCs) that you could share with us?
     
    #2 SFO, Jul 15, 2021
  3. nathandavidhall

    nathandavidhall Junior Member

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    Just checked with a Panlong Mini OBDII and Torque Lite, only got the P0420 code I already knew about ("catalyst system efficiency below threshold (bank 1)," this caused the check engine light to come on awhile back and seems like my googling showed this wasn't a big deal). I don't see any codes dealing with brake systems, though I don't know if having an out of date but still functioning app has anything to do with it (said it was made for an older version of android on startup). I just used the Fault Code search at the top of the menu in Torque Lite, searched both logged and pending faults
     
    #3 nathandavidhall, Jul 15, 2021
  4. SFO

    SFO Senior Member

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    Odd, given those warning lights there should be some stored OBD2 codes for retrieval.

    Did you load the appropriate prius gen2 PIDs into torque ? (this might apply if using an older version, or may be an issue regardless)

    You might also try Dr Prius or Hybrid Assistant, but check compatibility here : Hybrid battery diagnostic and repair tool for Toyota and Lexus

    Never tried it, but this app has been used by others as well.

    Seeing as you're interested in DIY, and since this involves the brakes, best to pick up a mini-vci cable (or better) and run techstream (dealer diagnostic and repair software) on a windows device (can emulate if needed).

    Is the brake accumulator 'barking' or making more noise than usual? (you'll hear this sound for a few seconds when using the brake pedal)
     
    #4 SFO, Jul 15, 2021
  5. nathandavidhall

    nathandavidhall Junior Member

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    For some reason Dr. Prius wouldn't connect to the bluetooth OBDII device, I used it on my '07 Prius to diagnose a couple of bad battery modules with no problem. Not sure why it wouldn't recognize/connect to bt OBDII in her '05 when Torque Lite did it just fine, I'll try again in a bit

    The PID thread you linked to is a bit confusing to me.. this Torque Lite has only been used on gen 2 Priuses so I would think it has the correct stuff loaded, I don't see anywhere in its menu to load PIDs or specific vehicle info.

    Will have to dig a bit on mini VCI cable, Techstream etc.. I like to do some DIY but there's always the decision point about whether it's better to just pay someone who already has the tools and skills, which of course is a factor of how high the shop cost is vs how much time/learning curve is involved with DIY. If a shop will be over $300 then sure I'll get a $40 cable and spend some time learning a new interface for a less than 3 hour job with less than $100 in parts, but if it's more like $150-200 at the shop then it's a little tougher to justify :p

    I didn't notice the "barking" you mentioned but I'll check it again in a bit
     
    #5 nathandavidhall, Jul 15, 2021
  6. ChapmanF

    ChapmanF Senior Member

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    There is an important feature built into the brake ECU that gets around all of the complexity of finding a suitable scan tool that will work and retrieve the codes. The ECU is built so that if you jump a simple wire between two pins at the diagnostic connector and turn the car ON, trouble codes will be blinked out at you on the dash warning lights; you just have to count the blinks. (A forum search here will turn up the details.)

    You can get strictly more information using a (working) scan tool, but when brake issues are present, the first order of business is making sure you find out why, and this feature means you can always do that right away, even if you don't have a scan tool handy, or the one you have isn't cooperating.
     
    #6 ChapmanF, Jul 15, 2021
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  7. nathandavidhall

    nathandavidhall Junior Member

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    Interesting, when I tried to search for that just now I just kept getting hits on jumping pins 4 and 13 to clear brake related codes that pop up after people do brake work, there were a couple of references to how it's actually for diagnosis and not for clearing but couldn't find anything on how to do it and what to count.

    That reminded me that the front left wheel bearing was replaced in this car a couple hundred miles ago, maybe it's a sensor issue related to that?
     
    #7 nathandavidhall, Jul 16, 2021
  8. ChapmanF

    ChapmanF Senior Member

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    Forgive me, sometimes I get weary of rewriting the same post, or trying to remember where I posted it last; I often end up doing the same search it seems like an engaged reader could be doing.

    You could try this one or this one or this one.

    It never fails to amaze me how many posts people can search up that only talk about a 'trick' for clearing the codes. Clearly all of these people have somehow heard of jumpering Tc to CG, and have actually done it, and have therefore had their car blinking the relevant codes at them while they ignored the blinking and thought "ok, what was that next step where I clear them?" and end up never finding out what their car needed to tell them.

    For whatever reason, those posts keep on replicating so fast there's no keeping up with them, and they make the ones about actually using the information to learn what's wrong with your car a little harder to find in the noise. There must just be that many people who somehow hope that clearing problem notifications will make problems go away.
     
    #8 ChapmanF, Jul 16, 2021
  9. nathandavidhall

    nathandavidhall Junior Member

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    Definitely appreciate it! Apologies that the noise was a bit too thick, I'll try to apply this approach and/or get the phone apps working better with the OBDII reader by this evening
     
    #9 nathandavidhall, Jul 16, 2021
  10. JoeB

    JoeB Junior Member

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    That is worth tracking down.
     
    #10 JoeB, Jul 16, 2021
  11. nathandavidhall

    nathandavidhall Junior Member

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    Ok, I have now done a few things:

    1) Paper clip jumpered pins 4 to 13, and I think I got the following codes: ((!)) 41, 44, 47. ABS: 42. Any help looking those up would be appreciated, haven't been able to find from googling

    2) Went on a test drive, noticed that car seems to have even less resistance when brake pedal is slightly depressed (just before brakes catch) than with no pressure on brake pedal. Once they catch they work great with no squealing or grinding, tried it on some steep hills and speeds around 50mph. Once they catch further pressure works as expected, solid breaking just later and weirder engaging

    3) Downloaded Car Scanner app (after trying Torque Lite and Dr Prius again, the latter doesn't do any codes with the free version apparently), got new app synced up (actually seems to give a lot more info with better interface than Torque Lite), still gave the same P0240 code as before. Even went through a detailed list of all sensors and couldn't find anything weird.

    Seems like I'll either have to figure it out from the paperclip morse code approach (was surprisingly challenging to keep pin 3 to 14 connection going), or may break down and get the mini VCI cable if those blink codes don't solve it. Found this manual here but I can't figure out how to look up the morse code translations in its 4000+ pages. Also wondering if this could be related to the wheel bearing replacement, could a pressure washing with that wheel off possibly solve it?
     
    #11 nathandavidhall, Jul 16, 2021
    Last edited: Jul 16, 2021
  12. SFO

    SFO Senior Member

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    After market sensors in wheal bearing assemblies have been known to fail, was the replacement a new OEM from the dealer?

    Best to do a visual/mechanical inspection before pressure washing.
     
    #12 SFO, Jul 17, 2021
  13. ChapmanF

    ChapmanF Senior Member

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    You're probably fortunate not to have found them from googling, considering how often random google hits for trouble codes are bad information.

    Just for the record, you meant pin 4 to 13. :) (Other people may find this thread from, ahem, googling, so we don't want to tell them the wrong pins and zorch their cars.)

    That's kind of explained in this link, the first one that I gave you upthread in post #8. It's handy to search in the PDF file for the two-digit blink code with a slash in front, because the codes are all listed with the five-character code you would get from a scan tool, a slash, then the two digit blink code.

    So when you search for /41 the very first hit that comes up is on page 1168 in the "DTC chart of ECB" table, as C1241/41. You have to glance up at the top of the table to make sure it's the one for ECB (since you said the ((!)) light was the one blinking this code) and it is, so you know that code is C1241. Looking down in the same table, you see the /47 from the same light is a C1247, pertaining to the stroke sensor.

    You might notice that you don't find the /44 in the ECB table where you might expect to, somewhere between the /41 and the /47. That's because the table is in order by the five-character DTCs, not by the blink codes. Down near the very end of that same table, you find C1378/44, pertaining to communication with the brake power supply capacitors in the back of the car.

    On your ABS light you only had the blink code 42. You don't find that in the "DTC chart of ABS" (a couple pages further back) at all, but that's also explained in that first link in #8, and also a little better here. The blink code 42 on the ABS light just means "hey, the ECB light has codes you should look at".

    The workup sections for those three DTCs start on pages 1201, 1215, and 1280 of the manual you found. Those sections will tell you exactly what the "DTC Detecting Condition" is for each code, that is, what the computer actually saw to make it set that code. You can see there are often three-digit INF codes that help you narrow down the details, but there aren't blink versions of those; a scan tool is needed to retrieve them. If you are working with blink codes only, you just kind of have to work through all of the given troubleshooting possibilities as if you don't know which specific INF codes you've got.

    Now that C1241 you've got means a low supply voltage was detected coming into the brake ECU. That does not always mean a problem with the 12 volt battery itself; as you can see from the listed trouble areas, it can also be in any of the relays, wiring, or connectors on the paths delivering the power to the brake ECU where the low measurement was seen.

    But as a first step with a code like that, you wouldn't be crazy to check the voltage and condition of the 12 volt battery, maybe even give it a good full charge or consider replacing it, then maybe clear these codes (you've already written them down, so they won't be lost) and see which come back. There are some members who reflexively go to the 12 volt battery for any codes at all, which seems excessive to me, but I'm happy to go there when you actually have an ECU saying "hey, this voltage was low."

    Sometimes, when people do replace or fuss with the 12 volt battery in back, they might unplug the connection to the brake capacitor box that's right next to it, and if that ever happened and wasn't completely plugged back in, that could be behind the C1378 you've got.
     
    #13 ChapmanF, Jul 17, 2021
    Last edited: Jul 17, 2021
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  14. nathandavidhall

    nathandavidhall Junior Member

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    This was done at a nearby independent shop with good google reviews for the best price i could find when I called around, around $250 vs $600-700 from other shops. Maybe that was due to using after market vs OEM? I could check with them but it was 2-3 months ago and not sure how good the record keeping is at this little east TN repair shop
     
    #14 nathandavidhall, Jul 17, 2021
  15. nathandavidhall

    nathandavidhall Junior Member

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    Definitely appreciate all the info! And d'oh on the pin typo, will correct when I'm on a pc (phone isn't letting me edit post for some reason).

    I'll check the voltage on the 12v battery soon, I replaced it about 2 years ago when the old one died and she hasn't left the lights on or anything else to drain it that I know of, I have a Norco smart charger I could put on it for the heck of it too.

    It sounds like the mini VCI + techstream would help to really get to the bottom of it, but would it be able to say if it's related to a faulty sensor associated with the wheel bearing replacement a couple months ago? Also, how dangerous is it to drive the car right now? I went pretty fast down some pretty steep hills yesterday and the brakes worked fine other than the weird behavior described, but I wouldn't want an actuator to suddenly fail due to not getting the right voltage or something in the middle of interstate driving
     
    #15 nathandavidhall, Jul 17, 2021
  16. ChapmanF

    ChapmanF Senior Member

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    There are specific codes for wheel speed sensors, and none of those are among the codes you have. If you had recent wheel bearing work done, it was natural to suspect it might be those as long as there was no other information to go on, but it's also natural to leave that hypothesis behind based on the codes you've actually got.

    As for safety, the system has a couple layers of fail-safe, and the second one is purely unassisted hydraulic braking that acts on the front brakes only. It will stop the car, but not gracefully, and won't have any ABS or stability features, so you might not rule out driving the car if you need to get somewhere, but you also might not put off getting to the bottom of the issue longer than you have to.

    The first layer of fail-safe relies on that capacitor box in the back of the car, so if that is unplugged or wonky, you might only have the second layer available.
     
    #16 ChapmanF, Jul 17, 2021
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  17. nathandavidhall

    nathandavidhall Junior Member

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    I already had my Noco 2amp smart charger out for a different Prius (my '07 with a couple of bad modules I'm planning to swap out soon had a dead 12v from sitting), so I disconnected the leads to the 12v battery in this '05 Prius and hooked up the Noco to it. Immediately showed a very low charge on its 4 bar status leds, over several hours it charged back up to full. Everything was hooked up correctly as far as the harness and multipin connector right next to the 12v battery, and I don't think she's been leaving dome lights on or anything. There seemed to be a bit of dullness/maybe corrosion so I hit the battery posts with some steel wool but otherwise I'm unclear about why the 12v battery would be low.

    Took it on a test drive, and unfortunately the full battery charge didn't change anything. I haven't checked it with a multimeter yet, but I would assume the full charge rules out the 12v battery as the culprit. So is it now a matter of getting the subcodes with a mini VCI cable and techstream to figure out if an individual relay somewhere has gone bad? Just ordered this one fwiw
     
    #17 nathandavidhall, Jul 18, 2021
    Last edited: Jul 18, 2021
  18. nathandavidhall

    nathandavidhall Junior Member

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    So the mini VCI cable came in, I smacked my head against a wall for awhile trying to get software to work, and finally back around to messing with it. If anyone could help me get this J2534 cable and Techstream working I would greatly appreciate it. I have tried following multiple instructions to no avail, including the ones that came on the dvd, from the more up to date zip file the seller linked to in an answer to a question on the amazon page, and from helpful reviewers on the amazon product page.

    The main problem is that none of the mini VCI driver install files ever finish, I always get the below result from all of the ones I've tried. I've been trying both on my 64 bit windows 10 (supposed to work on it if instructions followed correctly), also installed VirtualBox and Windows 7 32 bit but haven't had much luck there either. I'm not exactly a computer whiz but can usually follow instructions well enough, this has been quite frustrating though
     
    #18 nathandavidhall, Jul 31, 2021
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