Speed sensor faults causing ABS, brake and skid light

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by jeff galusha, Mar 24, 2022.

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  1. jeff galusha

    jeff galusha New Member

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    2011 Prius
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    Hey guys. Last week I was driving to work and when I went to set the cruise, it kicked out after a few seconds and then the ABS, brake and traction light came on. It stayed on the rest of the day. I went to the parts store and read codes and it was C1238 foreign material on right rear speed sensor and C0210 signal malfunction on same sensor. I thought alright, no big deal. Just replace rear hub. I ordered one and went on my way. The next day all the lights went away and I went on a trip of about 300 miles. All was good for the first 200 and lights came back on. Long story short, the lights come and go but now I am also getting the error codes for the left side also, C1239 and C0215. Now I am sort of questioning weather it really is a wheel hub and sensor. I just bought the car last November and I looked up the repair history last night. Both rear hubs were replaced 30000 miles ago. I am interested in your opinion of what else you think it could be. Do you think both hubs would be causing this intermittent failure? I measured the 12v battery voltage with ACC on at 12.5V. I cleaned up the connections from the sensor to the harness. I am at a loss and this is driving me crazy and I cannot afford a dealership. HELP!!!
     
    #1 jeff galusha, Mar 24, 2022
  2. tankyuong

    tankyuong Senior Member

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    12.5v seems low
     
    #2 tankyuong, Mar 26, 2022
  3. ChapmanF

    ChapmanF Senior Member

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    12.5 volts with ACC on is quite satisfactory, and is in no way a suspect for the codes you have. (If you were to look in the repair manual, you would see notes to charge or change the battery if you saw an open-circuit voltage below 11.)

    DIYing can be quite fulfilling and also save you a bunch of money compared to using a dealership. The key is, if you want to save the money you can't afford to pay the dealer, at some point you'll have to do the same stuff the dealer would do, yourself.

    The dealer would need to find out what the actual cause of the issue(s) is. The sensors in the hubs? The connectors? The wiring? It takes some good old-fashioned gumshoe work to make those decisions.

    You can find the steps for troubleshooting in the repair manual (more info). You'll need general tools like a multimeter.

    For something that is intermittent, one special tool (that you already have!) that can be very helpful is the "speed sensor check mode" that is built into the brake ECU. Dealers hate chasing intermittent problems just as much as you do, so the brake ECU is built with a special mode you can activate, where it reports speed sensor errors much more sensitively and aggressively, so that a lot of the time it will turn an intermittent issue into a repeatable one. Then, using that mode, you can try out possible fixes and know much sooner whether you are getting somewhere.

    Using that check mode, by the way, is one of the last official steps in doing any wheel hub replacement. If that was not done by whomever replaced the hubs 30k miles ago, that job was never quite completed.
     
    #3 ChapmanF, Mar 26, 2022
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