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Skid Control ECU Or Not? VSC/ABS/(!) Lights

Discussion in 'Gen 2 Prius Technical Discussion' started by Michael H, Aug 30, 2018.

  1. Michael H

    Michael H Junior Member

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    Here is my beautiful 2005 Prius (after my 08' suffered an accident), my favorite part about her is that she can't roll past 300k miles. I initially found her as a rough gem a couple years back (@ 170k miles) with a dead HV battery for only $700. Found a replacement HV battery from an 05-06?, as-is on craigslist for $300 and pulled it out with my cousin up in Detroit. She has only had new front brake pads and a mechanic did the front struts.

    She ~340k +/- miles now, and still runs *semi*-strong, just a few bugs and TLC repair expected with this many miles. Up til now (turn of 300k miles) my VSC/ABS/(!) lights are illuminate consistently, and sometimes the red explanation would be present (or turn on/off intermittently while driving). It would make braking a bit more difficult, as if regenerative braking had been disabled. You simply had to 'come to stops quicker'.

    The dealer has told me that the brake control (skid control) ECU needed to be replaced. After some reading, I've determined that the 04-05' years can be tricky about direct replacements on this issue (must have the right model number). If not, you can use a nifty program called TechStream. I am not aware of all of its capabilities yet, but am posting after what I've found.

    Upon inspecting each component ECU, I was returned with these errors:
    Air Conditioner:
    B1476 - A/C Inverter Load System

    Gateway:
    B1271 - Combination Meter ECU Communication Stop

    ABS/VSC/TRAC:
    C1247 - Stroke Sensor
    C1343 - Hydraulic System (RR)
    C1344 - Hydraulic System (RL)

    I have saved the datalogs and real-time information that was available for the C1247 Stroke Sensor. I have then proceded with clearing the logs under the ABS/VSC/Trac profile, and the lights on the dash proceeded to vanish. I am able to brake much easier and this has seemed to fix my issue? But I will of course follow-up with the sensor codes and see if something is wrong.

    ***I am primarily making sure that I actually have to replace the skid control ECU (already found a replacement for $35), before I embark upon the 1+ day journey involving bleeding my brakes. I would be confident that I could perform this, but want to verify the dealer didn't give a faulty quote since I got brakes done somewhere else.. :)

    I would like to redo the brakes and routers soon too. Using this TechStream program, could I replace the fronts or backs -- without causing me to be in a similar situation as before? I also plan to replace the front wheel bearings, as they are sounding bad (have them purchased). Ideally I want to make this a all-in-one day project for when I have to take off the front wheels/bleed brakes/etc (as I may access to a hydraulic lift).

    Any other maintenance items can be suggested, I'm sure she's due for trans axle, inverter, CVT, etc fluids. But is there a 'point-of-no-return' on Prii? Where certain high milage cars don't benefit from particular fluid changes?

    Also any advice and fixing the odometer to read correctly would be appreciated. Not sure if I can do this, or if the dealer is limited to it. I noticed one of the ECU's needed updating when I was in TechStream, but I couldn't find a way to install/load it.

    Thanks in advance!
     
    #1 Michael H, Aug 30, 2018
  2. JC91006

    JC91006 Senior Member

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    $1000 for 170k miles seems pretty good. Maybe you can sell it for $1000 and find another gem again?
     
    #2 JC91006, Aug 30, 2018
  3. ChapmanF

    ChapmanF Senior Member

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    In a Gen 2, the skid ECU just lives under the dash. No hydraulics connect to it, no air gets in when you swap it.

    But honestly, nothing you posted explains to me why anybody thought you should swap it. It gave you some information about the stroke sensor and the rear hydraulic circuits. Replacing it because it gave you that information would be a shoot-the-messenger sort of repair.

    If it happens to come back with those codes again, I would thank it, and take a closer look where it's suggesting to look.

    -Chap
     
    #3 ChapmanF, Aug 30, 2018
  4. Michael H

    Michael H Junior Member

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    After searching on C1247, I came across this forum C1247 ECU Skid Control replacement? | PriusChat and their mechanic seemed to quote the same part for the Skid Control ECU. Given their problem was not resolved until actually replacing the stroke sensor (what was actually wrong). Interesting how the shops don't seem to quote the right work, and told me the ECU replacement was estimated at 8 hours. And 3 hours per tire to replace the bearings, lol.

    Brake, !, ABS, & VSC Warning Lights. Techstream says DTC C1343 | PriusChat This also seems to be a very similar situation as to what I am facing. Does RR stand for Right Rear Side? Maybe the back brakes were worked on or checked by another mechanic. Is there a way to reset the brakes myself without actually replacing them? Or should I replace them just to be safe?

    Should I even worry about replacing the brake position sensor? From some on ebay for about $30. But if the problem doesn't come back (like a normal error code), should I even bother? Thanks
     
    #4 Michael H, Aug 31, 2018
  5. ChapmanF

    ChapmanF Senior Member

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    Good research. The find-out-what-might-be-wrong part isn't far enough along yet to be anywhere near talking about replacing stuff. Just keep checking out what the system is telling you about what might be wrong.

    Yes, RR is rear right, RL is rear left.

    When you look codes up in the repair manual, each code leads to a section (usually from one to eight pages or so) of what you should check to find out why that code was set. The section will start with a little box that gives the "detection condition" for that code.

    The detection condition tells you exactly what the computer has to sense to trigger its programmed response of setting that code. It's a lot more useful than the sort of fortune-cookie one-liner for the code that might pop up on your scan tool.

    For example, a code that's about your stroke sensor is not a code that tells you the sensor is bad and you have to replace it. There's no way the computer could know that, it's trapped in a box and it can't climb out and go poke at the sensor to see what's happening.

    All the computer knows is that something about the signal it receives from the sensor is unexpected in some way. (The detection condition in the manual will tell you more.) It's up to you to do the poking. Did you kick the plug out of the sensor? Is it hanging on by a bent bolt? Does it need to be adjusted? The pages in the manual for the code will have ideas for how to work through the possibilities.

    Likewise, having a code about the RR or RL brakes is not like a mission from God to go replace the RR or RL brakes. It's just about looking in the manual to find out what the computer must have seen to give you that code, then you get some tools and your flashlight and go find out why it saw that, and what needs to happen to fix it (which could involve replacing something, or could very well not.)

    -Chap
     
    #5 ChapmanF, Aug 31, 2018
    ITBland likes this.
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