ABS, VCS, (!) light intermittently appears, despite new sensor.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by dproch123, Aug 7, 2018.

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  1. dproch123

    dproch123 New Member

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    Hello All,

    I have a 2009 Prius with ~185K miles, and the ABS, VCS, (!) light continues to pop up - I believe, randomly. It seems to happen more when I am on the highway, but it has happened at slower speeds.

    There is no brake light associated with it. Also, I have the techstream software - bought it on Ebay - which diagnosed the issue as C1235 (C1235 TOYOTA Foreign Object Attached On Tip Of Right Front Sensor).

    From there, I cleaned the sensor, put it back, and cleared the code. It subsequently came back on again.

    Next, I bought a used, but functional wheel sensor and swapped it out. I cleared the code again, and the same ABS, VCS, (!) light appeared.

    At this point, I am at a loss. I'd rather avoid taking it into the dealer if possible, so, does anyone have any ideas? Might it be the actual control board that is receiving the signals from the sensor? Would changing the bearing/hub possibly take care of this?

    Any help would be much appreciated.

    Thanks in advance.

    David
     
    #1 dproch123, Aug 7, 2018
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The problem is either the speed sensor, or the wiring harness connecting it to the skid control ECU, or dirty/damaged teeth on the sensor rotor, or the skid control ECU itself. I suggest you remove the sensor again and rotate that hub while looking through the sensor hole at the toothed sensor rotor. If there is any dirt on the rotor, clean it using brake parts cleaner. If there are any chipped teeth, then you would have to replace the axle hub.

    To test the wiring, you would have to measure resistance from the speed sensor wiring harness connector to the skid control ECU, which implies you have access to the electrical wiring diagram so that you can figure out what ECU wiring harness pins to measure. Finally if you can't find any other problems, you could try replacing the ECU with a used unit and see what happens. Good luck.
     
    #2 Patrick Wong, Aug 8, 2018
  3. dproch123

    dproch123 New Member

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    Patrick, thanks so much for the quick reply. I will pull the tire and check the rotor and hub. Any idea as to where, specifically, the skid control ECU is located in the vehicle? There doesn't seem to be a lot out there with respect to replacing that (which, hopefully, it won't come to that).

    Thanks in advance.
     
    #3 dproch123, Aug 8, 2018
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