Brake Pedal Stroke Sensor

Discussion in 'Gen 2 Prius Technical Discussion' started by dhman2006, Aug 8, 2020.

  1. dhman2006

    dhman2006 Member

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    Few days ago while I was driving my ABS, VSC, Brake and (!) signs came on along with a high pitch noise. My brakes also started feeling very light. Lucky for me I was only few minutes away from home and using the emergency brake I got home safely. I haven't driven the car since then, but as soon as I step on the brake/ try to stay the car that high pitch noise comes on and the signs come on as well. I tried resetting (by connecting the OBD 4 and 13 pins) just to see if I got a faulty signal, but that didn't work. So I did some digging here and it looks like it could be the Brake Pedal Stroke Sensor. So I looked at my stroke sensor and it looks like the black handle of the stroke sensor that attaches to the brake pedal is working fine, but there's a white piece on the stroke sensor (please see attached picture) that doesn't seem to be doing anything unless I'm manually moving it by hand. I called toyota and got the part number for that sensor (89510-47010) and looked up a picture of it online. It looks like it's supposed to be moving with the black tip and the pin that connects the white piece with the black tip somehow broke off. So I was wondering if anyone know has any experience with this and if my observation seems valid. If the white piece is missing a piece than I think just replacing the stroke sensor will take care of my issue and should be a relatively inexpensive solution for me.



    89510-47010_1.jpg
     
  2. ChapmanF

    ChapmanF Senior Member

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    I've never looked at one that closely, but the installation instructions in the manual refer to mounting the sensor in place, then stepping on the brake in order to break off the pin that holds the sensor at the calibrated zero point during shipping and installation. Your picture looks very much like it could be that pin, in which case you would expect it to be missing. If you look closely at that whole white piece, it looks just like an external part they could slide at the factory to the exact zero-calibration point for the sensor, then tighten that screw to hold that position.

    If you are getting the alarm beep, I don't think you have a stroke sensor issue. You can look in the repair manual (more info) and find a table of the brake system trouble codes, indicating which few of them also set off the alarm. Those are generally limited to the ones needing to warn you about low hydraulic pressure and the chance you might need to press really hard to slow the car.

    Have you read the trouble codes yet? It would be a good place to start.
     
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  3. dhman2006

    dhman2006 Member

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    Thank you for sharing the repair manual link. I connected a Autolink AL319 OBD scanner to the car but it couldn't find any code. That's why I was wondering if that white piece is supposed to move with the black tab. In the absence of a code, I'm not sure what else can be causing this issue.
     
  4. ChapmanF

    ChapmanF Senior Member

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    If you search around forum threads here, you can find people's favorite solutions for reading Prius trouble codes (the ones that actually work, so we don't end up with "but there are no codes" questions). Some of them cost very little, especially if you have a spare old laptop to use.

    While waiting for delivery of any of those options, there is always a way you can get the brake system codes, without any reading device at all. You already almost did:

    If I had a nickel for every time somebody posts on here that they think the purpose of connecting pins 4 and 13 is to reset something ... there must be some really popular sources online somewhere giving everybody that idea.

    The purpose of connecting those pins is to read codes. When you do it (and the car power is on), dash lights start blinking. You can count the blinks into two-digit codes that are listed in the manual. It's like an abridged form of the five-character trouble codes you would get from a scan tool.

    As soon as the codes are known, is often easy to complete the picture of what is going on.
     
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  5. dhman2006

    dhman2006 Member

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    I'll try getting the code that way. Any idea when the scanner isn't showing any code?
     
  6. ChapmanF

    ChapmanF Senior Member

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    Non-Techstream scanners are sort of wild cards. Did you scan for codes at a time when warning lights were present on the dash? If so, there were codes. Simple retrieval of DTCs isn't supposed to be any fancy manufacturer-specific thing, especially from the brake ECU, which is at a standard address in every car. So there shouldn't be scanners that don't see brake codes.

    And yet, people report it. Maybe it would be possible to figure out just why scanner X failed to retrieve codes that it should have been able to retrieve. But without that kind of time to spend on it, often the solution comes down to not using scanner X.
     
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  7. dhman2006

    dhman2006 Member

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    Is there any manual that explains how to read the code? I tried to get the code by connecting the 4 and 13 pins, but I have no idea how to read the code. Hoping someone on this site can help me decode this ---

     
  8. dhman2006

    dhman2006 Member

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    Yup. The scanner was hooked up right when the codes were present. However, nothing could be found
     
  9. ChapmanF

    ChapmanF Senior Member

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    The repair manual does. Link shared above.
     
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  10. ChapmanF

    ChapmanF Senior Member

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    You have to focus on one of the lights at a time, and not let the others make you lose count. The ((!)), ABS, and VSC lights are all blinking out their own codes. The ((!)) light is blinking 53 and 57. See it?

    Then you just ignore that one and move on to the next. It's important to remember which codes were blinked on which light, because they are in different tables in the manual (even though all three lights are driven by one ECU, it's like it has different functional departments). Some of the numbers might overlap, so matching one in the table for the wrong light can lead you astray. (That can easily happen if you have the manual in a PDF and you do a search for a code number, and it takes you to a match but you don't look up at the top of the table to make sure it's the right one.)

    Speaking of searching in a PDF, they usually typeset the numbers as the five-character DTC that a scan tool would show you, a slash, and the two-digit blink code, something like C1241/41 (the blink codes aren't always the low digits of the DTC, but sometimes they are). That's helpful, because as you can imagine just searching for 41 in a thousand-page manual will take you all over the place, but searching for /41 will usually get you where you're going.
     
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  11. dhman2006

    dhman2006 Member

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    Thank you! I think I'm seeing 53 and 57 for ((!)), 42 for ABS, and 45 for VSC. Please let me know if you see anything else.

    Per the PDF, 53 and 57 show common theme for Harness and connector and Brake actuator assembly; 42 is showing Open in IG1 / IG2 Power Source Circuit and 47 is the stroke sensor malfunction. If the white piece is supposed to be moving freely, I'm leaning towards loose harness somewhere or replacing the ABS fuses for C1253. Not sure about the open IG1/ IG2, but will do some digging. Thank you for your help so far
     
    #11 dhman2006, Aug 9, 2020
    Last edited: Aug 10, 2020
  12. ChapmanF

    ChapmanF Senior Member

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    It looks like you've found the short summary table near the front of the brake section. It's ok, but the summaries are really too short. You can see there's a "See page" column in it, for every code, takes you to the start of a whole section for that code. Every one of those sections starts with a box containing the "detection condition", which tells you the exact conditions the computer had to see to make it set that code. That's really the meat of the whole affair; people sometimes talk about a code meaning "oh, there's a problem with X" or "you need a new X", but in reality, with the computer being a dumb automaton trapped in a box, the only thing any trouble code really "means" is what the computer saw when it set the code, and that's the detection condition that heads the workup section for the code.

    You can get there quickly by repeating the search for the blink code with slash in front. After that summary table you found, the next occurrence is usually the workup section you're looking for.

    For example, if you look up the 57 code, you'll see it can mean two different things (depending on the INF code, which unfortunately you can't get by blinks; you can read it with Techstream). Say you read inf 141. Now you know you have this code either because you tried to brake once, when the car was moving, and there was less than 12.45 MPa pressure available to assist you, or, within two minutes after starting the system, it hasn't been able to make at least 14.62 MPa pressure.

    You said you heard the buzzer. It's these hydraulic-pressure-related codes that will trigger the buzzer. The other codes are probably not why the buzzer sounded.

    You mentioned reading 45 for VSC, but later on you say 47 for the stroke sensor malfunction. I just watched your video again and I agree with your first count ... I get 45.

    In the Gen 2 manual I happen to be looking in (a 2006, not your 2005), there is no 45 listed in the VSC table. That does happen sometimes; Toyota uses their Techstream and the 5-character trouble codes most heavily, and it seems like the blink codes in the manual don't get a whole lot of editorial love, and some turn up missing. There's a 45 in the ABS table, but that's the wrong light. And the 47 you found is in the ECB table, not VSC. It does say stroke sensor malfunction, but that's a code you didn't get, and would be in the wrong table if you did. :)

    The big concerns are your 53 and 57. As you see, for the 57 it would help you to know which of the two INF codes you've got, and for the 53 it would help you even more to know which of the seven INF codes went with that one. That generally means finding an old laptop to run Techstream on, or somebody who has one.

    You might be weighing your wallet right now, thinking that hydraulic pressure problems can mean replacing the actuator. And yes, they can, but there are parts of this picture you haven't filled in yet.

    One is your 42 code. The braking system in Gen 2 is split in redundant twins, each one getting its own 12 volt power (at the IG1 and IG2 terminals, unimaginatively enough). Depending on which of the two INF codes you got with 42, something odd happened one time when you got in the car: either IG1 got voltage 4 seconds or more earlier than IG2, or, IG2 got voltage 4 seconds or more earlier than IG1.

    Needless to say, that's weird; they should get powered up at the same time. That suggests some flaky power delivery to the brake unit, which can easily come down to things like corroded wiring connectors, with fifteen year old cars in places like Boston.

    And flaky power delivery to the unit could certainly explain it failing to build adequate pressure in the allowable time.

    So that would definitely be stuff to check out before assuming it's new-actuator time. (You might be thinking there's not much worse than replacing an actuator, but there is: worse is replacing an actuator and then having the same problem because it was really something else all along, and way worse is when the something else would have been cheap to fix.)
     
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  13. dhman2006

    dhman2006 Member

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    Thank you for your input. I don't think it's actually the actuator. I found this video (
    ) that shows symptoms for the actuator problem and my car isn't making the noise that usually indicate actuator issue. I'm assuming it's loose wire/ connector or fuse somewhere along the line.

    So after work today I started with engine compartment fuse boxt and found that the 25A fuse that's for ABS−1 in the Gen 2 prius is blown. So I replaced it and the beeping noise went away, but after 2 different starts the beeping noise came back again. It looks like there are few other ABS related fuses, but one of the fuses seem to be in the white compartment of the fuse box. Not sure how to remove box. So next step will be trying to figure out how to get fuses out of that thing
     

    Attached Files:

  14. ChapmanF

    ChapmanF Senior Member

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    I think the white thing is an integrated multifuse assembly—great timesaver at the factory, kind of a headache under the shade tree. Does it look like any of its fuses are blown?

    What was the fate of the ABS-1 fuse you replaced? Has the replacement stayed unblown?

    Do you have access to the wiring diagram to see what ABS-1 feeds?
     
  15. dhman2006

    dhman2006 Member

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    I didn't really have much time to look at the multifuse assembly, but hoping to get out of work soon tomorrow to look at it.

    The ABS-1 fuse stayed unblown which I'm taking as a good sign.

    I'm hoping to go through the pdf files to figure out what ABS-1 feeds. Hoping to find that tonight before I hit the bed. I'll use the PDF file along with this link to figure out which ABS fuse is doing what --- '03-'09 Toyota Prius (XW20) Fuse Diagram
     
  16. ChapmanF

    ChapmanF Senior Member

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    A followup on this thread concerning the few 'mystery' blink codes that can't be found in some editions of the Gen 2 manual (36 on ECB, 42 on ABS, 43 or 45 on VSC): more here.
     
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