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Is my exciter ring damaged enough to cause issues?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by dragonrand, May 3, 2014.

  1. dragonrand

    dragonrand Junior Member

    Joined:
    Nov 29, 2007
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    Location:
    Springfield, MO
    Vehicle:
    2005 Prius
    I've been thru several wheel bearings (hub assemblies, actually) in the last 15 months and just had another replaced under warranty. (The whole story is in this thread.) Short version, I had them put a Toyota bearing in this time, after which they told me my speed sensor was now damaged. I had them replace that (they used aftermarket) and have been driving the car for a week now, but I've noticed that traction control still momentarily kicks in under normal braking now and then. It has even failed and disabled itself completely once since the sensor was replaced.

    I was back at my tire shop today for other work. I asked them to check the exciter ring on the wheel where the speed sensor had been damaged, while they had the car up. Here is what we found:

    IMG_2957.jpg

    IMG_2959.jpg

    Is that damaged enough that I would experience some inconsistencies when braking? I don't know what the tolerances are for these sensors. I've been quoted a new half shaft at just under $350 installed, and I'm strongly considering it. I'll have my tire shop do the work, not my (formerly) regular mechanic.

    As luck would have it, the guy I was talking to at my tire shop worked in Toyota service for several years. When I told him I'd had two new bearings fail within the space of 6-9 months, he speculated that the aftermarket bearing itself might have been fine, but that guys at my shop were probably not bothering to check the torque specs and were thus over torquing the hub assembly. After what I've been through at that shop, it seems plausible enough. I disovered today that the dust/debris cover for the exciter ring wasn't replaced at some point during all the recent work on this wheel (driver's-side-front). It's completely missing, while the cover on the passenger front wheel is still present. I'm getting distinct impression that this shop, while honest and committed to making me happy, isn't the best at paying attention to details, even when they're potentially important.

    Is replacing the half-shaft to get a clean new exciter ring a worthwhile thing to pursue? All opinions appreciated - they're probably much more informed than mine.

    Thanks!
     
    #1 dragonrand, May 3, 2014
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    18,200
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    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    It looks like someone used a pry lever to separate the half-shaft from the old hub, which is very poor service practice and caused the damage. The old cover was probably also damaged in this process and also needs to be replaced.

    Yes, you need to replace the half-shaft since you need the braking system to operate correctly.

    The repair manual specifies that the signal from the sensor when measured with an oscilloscope should be ~5 volts sine wave, peak-peak, at 19 mph speed. Also see the following note regarding the speed sensor rotor:

    As the vehicle speed (wheel revolution speed) increases,
    a cycle of the waveform narrows and the fluctuation in the
    output voltage becomes greater.
    When noise is identified in the waveform on the oscilloscope,
    error signals are generated due to the speed sensor
    rotor’s scratches, looseness or foreign matter attached

    to it.
     
    #2 Patrick Wong, May 3, 2014
  3. KhaPhoRa

    KhaPhoRa Member

    Joined:
    Feb 7, 2013
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    Vehicle:
    2006 Prius
    Model:
    II
    Yeah that's going to be a problem, and a problem with the VSC and ABS isn't one I would want to drive around with. Between that and the obviously damaged sensor I would avoid the old place at all costs. As a side note I just discovered a toyota dealership didn't replace a dust shield on my passenger side bearing hub. It was done six years ago before I owned the car, and it's been fine. I replaced the hub on they side just because I had purchased two when my drivers side failed. It's a pretty easy job and isn't hybrid specific (my wife's minivan was an identical procedure, just larger parts and a bearing to press out) so the fact they screwed it up and took unnecessary short cuts in the process is all you should need to know about using that shop in the future.
     
    #3 KhaPhoRa, May 3, 2014
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