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Skid sensor alarm, can't accelerate

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by crockettor, Sep 20, 2013.

  1. crockettor

    crockettor Junior Member

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    When I hit about 45mph the skid detector light goes on, the car beeps like crazy, and the accelerator will not work until speed has been reduced to about 25mph. This is on dry road, definitely NOT under skid conditions.

    History: Front driver's side rim and tie rod were damaged. New tie rod was installed and I drove it on the spare tire just fine. The Tire pressure monitoring system light was on, but no skid warnings.
    I bought a replacement rim, had a used tire put on to match the tread of the current tires. I then took the car to get an alignment. After that I experienced the skid control problem.

    I told the alignment shop about the problem and they indicated that the TPMS and skid sensor alarms may be connected, and that the 1 replacement tire may be causing the problem. I went home, rotated that tire to the back, and did a test run. 10 miles, 60mph, no problems. Next morning I'm heading to work and the skid problem comes back, and I'm stuck doing 25 on the highway.

    Any ideas? Would a TPMS alarm set off the skid alarm? I understand that the TPMS sensor in the rim was not changed to the replacement rim, but would that affect the skid sensor? I was under the impression skid control only measured difference in drive shaft rotation. I really need this car to go over 25! :eek:)
     
  2. Britprius

    Britprius Senior Member

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    Is the new tyre the same size as the rest of your tyres as this will cause the problem. You say the tread matches but do not give the size of the tyre fitted or the OEM size.

    John (Britprius)
     
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  3. edthefox5

    edthefox5 Senior Member

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    Its seeing different rotational speed of the tires. John's probably right.

    Or the ABS sensor is askew somehow and not reading right.

    You also may have a damaged wheel bearing or a caliper is hung up.

    Also as a side note look at where the inner cv shaft enters the differential of the cvt too. Sometimes a wheel hit will damage that seal there and the trans fluid will leak out and toast the tranny. See if there's any fluid leaking from the inner shafts seal at the trans both sides. You'll never know unless you look.

    TPMS would not cause your issue, it will just throw the yellow tire in parenthesis icon on dashboard.
     
  4. crockettor

    crockettor Junior Member

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    Thanks for the replies so far. The wheel was replaced with an identical 15" OEM rim with a matching 185/65 OEM size tire with about the same wear pattern as the other wheels. It is a Bridgestone and the others are goodyear integrity, but I thought matching the wear would be better than getting a new tire of the same model.

    I bought this car at an auction and it's my first prius, so I'm learning the ins and outs. It was hit on the front drivers wheel. The CV shaft was also replaced, along with the suspension arm, inner/outer tie rods, suspension strut, rim, and tire. It sounds to me like a bearing could be going out, but the mechanic said that sound could be coming from the regenerative brakes. I'm not convinced he knows much about the prius, though. The old CV shaft was ok, but the boot was damaged and trans fluid had leaked, so I opted to take the mechanics recommendation and replaced the whole thing instead of just the boot. No leaks now, everything looks good, although when I grab the shaft I can move it slightly, maybe a half a millimeter. I didn't think that was right (tried to move the other side, and checked my other cars and none of them jiggled), but the mechanic said that could be normal.

    So the ABS sensor is connected to the skid warning? Is that located on the brakes somewhere? I would buy that it was knocked askew in the collision. Or that the caliper is a little goofy. Should my next stop be the brake shop?
     
  5. crockettor

    crockettor Junior Member

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    I should also note that after the problem appeared I rotated the replaced tire to the back to ensure that it was not causing any problem in the front end. So now the front tires are matched. Is there skid sensors on the rear wheels as well?
     
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Each wheel has a speed sensor, which are monitored by the skid control ECU.

    Check the tire pressure on each tire. Even if you had checked this previously, pls do it again. Maybe a tire has a nail in it. Low tire pressure will result in a smaller circumference, thus forcing that tire to rotate faster than the others.
     
  7. crockettor

    crockettor Junior Member

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    I have all tires at 35psi.

    I decided to run a test tonight. I found the ABS speed sensor and disconnected it on the drivers side front. Pretty easy to do, it's just an little electronic push pin at the top of the inside of the fender. Now the dash lights show ((!)) ABS VSC, but the car will no longer refuses to accelerate. Problem solved? Well, the alarm still goes off between 45 and 55mph and beeps like crazy, but oddly enough the skid light never comes on. Could it be the sensor is busted?

    I will take the sensor off tomorrow and take a look at it to check for visible damage. A new one is about $150 from RockAuto so I may just try throwing a new one on to see if that helps. I'll call around a few shops to price it out too.
     
  8. nh7o

    nh7o Off grid since 1980

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  9. crockettor

    crockettor Junior Member

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    20130921_135213.jpg 20130921_135451.jpg 20130921_135555.jpg 20130921_135608.jpg
    Ok, I tried pulling the sensor. It looked dirty, so I cleaned it. Otherwise it looks good, no visible damage. No change in symptoms though. The part number is specific to each wheel and they are not interchangeable.

    Would there be any visual indicator of the speed sensor being damaged?

    nh70 - I put the jumper on #4 and #13 on the obd2 port and put the car in Ready. A lot of things were flashing and it seemed too complicated to describe, so I'll take a video and post later.
     
  10. nh7o

    nh7o Off grid since 1980

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    Count the number of blinks for each of the icons.
    They blink in pairs, i.e. blink-blink-blink......blink-blink = code 32.
     
  11. crockettor

    crockettor Junior Member

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    I think I got it. 36 is 3 blinks, 1/2 second pause, 6 blinks, 2 1/2 second pause and it repeats over and over.
    ((!)) reads 36
    ABS reads 32
    VSC reads 43
     
  12. nh7o

    nh7o Off grid since 1980

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    ABS 32 confirms that the LH front speed sensor circuit is not working. If you are sure about the other blinks, I don't see those numbers listed. But start with the speed sensor and go from there. The speed sensor is just a coil of wire that responds to magnetic pulses from the spinning sensor rotor (which can be seen at the bottom of the sensor mounting hole in your photos). You can unplug it and check resistance: ~1.4K-1.8K ohms. Make sure that it sits totally flush in its mounting. It won't be affected by dirt. The picture looks OK.

    The connector in the last picture which is unplugged, that is where to check resistance. You could also swap the front sensors and see if the problem goes to the other side, where the ABS blink code would be 31. If not then the problem could be in the harness to the brake ECU.
     
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I agree that the sensor resistance should be checked. OP says the LF and RF sensors are not interchangeable since they have different part numbering.

    Since we know that the problem started after an accident impacting the LF wheel, I suggest that the toothed wheel (the LF sensor tip is positioned nearby) should be carefully inspected. Compare to the toothed wheel in the RF hub.
     
  14. nh7o

    nh7o Off grid since 1980

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    The part numbers are different, but they do have the same connectors, same resistance, and same mounting holes. The pigtails are routed differently, but it still might be possible to swap them for a small test run.
     
  15. crockettor

    crockettor Junior Member

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    My first instinct as well was to swap the front sensors and see if anything changed. They do look identical, other than the LF is orange and RF is green, and part numbers are different. I'll check the resistance, swap them, and report back. I can get a new sensor for ~$160 from toyotapartszone, or I've seen some used on ebay for $60 and up.

    I did not think to compare the toothed wheels. From what I could see in the left one, it looked to be ok, but perhaps it is slightly out of position. I will compare to the right side.

    I was going to post a video of the blinks here, but the site wouldn't allow it. I'll upload it to youtube and post the link.
     
  16. hlunde

    hlunde Member

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    There is no exacting industry standard for tire diameter. Different manufactures' tires may have different diameters. I know well from having to match tires on an AWD vehicle (Audi). I would take both tires off and measure circumference with a tape.
     
  17. Joe 26

    Joe 26 Member

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    Agree with above. Tires of the same size but different models or makes can have significantly different circumferences. Blow them up to the same pressure and run a tape around the circumference. Anything more than .25" difference has the potential cause an issue.
     
  18. crockettor

    crockettor Junior Member

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    The TPMS light is solved. The replacement rim did not have a TPMS sensor and the place I got the used tire at didn't tell me. They don't do any programming there. I took it to America's Tire and they installed a TPMS sensor and programmed it for $50.

    I will check the tire circumference, though. The Bridgestone Potenza seems to have a flatter surface area i.e. more contact with the pavement while the Goodyear Integrity is more rounded like a doughnut. The Bridgestone is marketed for better road gripping performance, and the Goodyear is a all season tire. According to my measurements the Goodyear is 1/8" smaller than the Bridgestone. I wrapped a string around the outermost tread, made a mark and checked it twice. The new TPMS doesn't appear to be having any issues with it now.
     
  19. crockettor

    crockettor Junior Member

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    Here's the video showing what happened when I retrieved the blink codes
     
  20. Britprius

    Britprius Senior Member

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    I only get a black screen with this vide0 is private.

    John (Britprius)