Parking brake/ABS/VSC lights stay on?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by mercat68, Feb 16, 2018.

  1. mercat68

    mercat68 Active Member

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    Started the 2007 yesterday and found that the parking brake light and the row of lights for tire pressure/ABS/VSC stay on. The car feels like it's dragging a little in drive, too. Any guesses? ABS system on the fritz? I put a code reader on it, but no codes reported. Thanks.
     
  2. mercat68

    mercat68 Active Member

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    Following up on my own post, I did find other threads on this exact issue, but not clear on a consistent cause. I did the diagnostic trick of jumpering TC & CG on the OBD connector and recording the flashes for tire pressure/ABS/VSC, and this is what I got:

    tire pressure: 36
    ABS: 31, 32, 33
    VSC: 43

    Hope that helps my fellow backyard mechanics out there. Thanks.
     
  3. edthefox5

    edthefox5 Senior Member

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    Go get the codes read. Autozone will not cut it as there readers are not fully hybrid capable. It may be the ABS unit has failed and if so the brakes will feel really bad. There's a time sensitive TSB out for it and they may grandfather you in for the repair. Get to the dealer asap tic toc.
     
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  4. edthefox5

    edthefox5 Senior Member

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    Go get the codes read. Autozone will not cut it as there readers are not fully hybrid capable. It may be the ABS unit has failed and if so the brakes will feel really bad. There's a time sensitive TSB out for it and they may grandfather you in for the repair. Get to the dealer asap tic toc.
     
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  5. mercat68

    mercat68 Active Member

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    Thanks!
     
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. Since you own three Toyotas, invest in Mini VCI which will read DTC on all Toyota vehicles.
    2. Check the air pressure on all four tires.
    3. The ABS blink codes imply you have a problem with three wheel speed sensors (RF, LF, RR) which seems improbable.
    4. Check the condition of the 12V battery.
     
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  7. edthefox5

    edthefox5 Senior Member

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    Hey pat where you been lol? Miss your posts dude.
     
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  8. edthefox5

    edthefox5 Senior Member

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    I have a driftwood 07 too.
     
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  9. mercat68

    mercat68 Active Member

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    Thanks. Air pressure’s fine on all four, and battery is new as of last fall (and I checked connections and voltage this morning, and found both OK). Is this likely the ABS ECU if multiple wheels are showing a fault?
     
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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  11. ChapmanF

    ChapmanF Senior Member

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    wss.png

    (I pasted from the section on the rear sensor codes; the front section is similar.)

    The four wheel speed sensors start out at very distant corners of the car, but the wiring circuits get closer and closer together until they plug into the same skid ECU at the same connectors, so if there are codes for three of them, there's probably something going on nearer that end.

    There are about 12 pages in the RM suggesting a good troubleshooting approach ... start non-invasively, using Techstream to watch the reported values and any error indications in real time while (somebody else is) driving the car ... move on to measuring voltages/waveforms right where the signals enter the ECU (still without tearing anything apart) ... proceed from there as the evidence directs.

    -Chap
     
  12. mercat68

    mercat68 Active Member

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    To close the loop on this: I took the car to a mechanic today. They found a bad right rear wheel bearing, which somehow triggered the ABS light by interfering with the sensor (?). Anyway, everything back to normal. Needed new brake shoes, too. The factory shoes finally wore out after 203,000 miles ;)

    Thanks again, everyone, for the advice.
     
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  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I suppose that a wobbling bearing would cause bad signals to be produced by the speed sensor.

    Interesting that the front wheel sensors also had fault codes logged. Glad to hear your car is restored to correct functioning.
     
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  14. ChapmanF

    ChapmanF Senior Member

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    I'm looking at the detection conditions in #11 and wondering if, where the comparisons of wheel speed signals are concerned, there might be a situation where the ECU can see that the readings are different, but not be sure which one's wrong. It doesn't jump out at me, and even on turns, I bet the ECU knows the car's geometry and how different the wheel speeds should be. Still, I wonder if that could be part of the story.

    -Chap
     
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  15. mercat68

    mercat68 Active Member

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    Good theory! That's why I love forums like this.
     
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