2002 Steering Wheel shutter?

Discussion in 'Generation 1 Prius Discussion' started by SteveWlf, Nov 10, 2012.

  1. SteveWlf

    SteveWlf Old-on-Hold

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    Only had this car for about a month and 1200 trouble free miles. Really in great shape but with 276K miles on it. Really runs great and feels like a new car inside and out.

    Yesterday, a cool morning, 38 deg.. Started at the Ready, backing out of my car port and cut the wheel partially to turn 90 deg. to enter the street. Came to full stop and shift lever is still in Rev., before I could shift to Drive. the steering wheel shutters like I was going over a rough. jerking lightly from left to right about 2-3 degrees. Stopped withing about a second and I still had normal steering response. I continued onto the street and made a ran a 300 mlle round trip on freeway and surface streets without any further problems.

    I know the power steering is electric assist over mechanical linkage and can only imagine that there was a power glitch in the power convertor and I was feeling pulses from the feed back in the power steering drive. No hydrolics to blame, I don't think.

    Any ideas or experience with the electric or mechanical portions of this type of power steering??

    Thank,

    Steve
     
  2. tochatihu

    tochatihu Senior Member

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    Hi Steve, this is not an unusual problem, and you will find a lot of discussion in the archives. There are position sensors similar to variable potentiometers that get noisy. The electromechanical system amplifies that noise, and it happens more often in the cold. Your options:

    Ignore it. Eventually it is likely that the EMPS will shut itself off (accompanied by an screen error message). Quite drivable at highway speeds, but parking and low-speed maneuvering will require arm strength. As such, not really a safe operating mode.

    See if Toyota will replace for free. They have done this in the past, the warranty enhancement had a sunset date, but others have got free replacements more recently.

    If you pay for a new replacement installed, I am sure you won't like the price. Less than $2000, but not a lot less.

    There are takeouts available from salvage dismantlers. I suppose the ideal would be from a 2003 that had not had front-end damage. Here the issues are whether the item would come with guarantee, and who would do the R&R.

    One might imagine that only the faulty part itself could replaced, but the design does not allow that. In contrast, a similar problem in the accelerator pedal is quite readily fixable, and the latest information there indicates that there are two different ways to fix. The throttle position sensor also uses the same technology, and it is a mystery why that one does not also get sick this way. Or perhaps it does and we never notice that it flails through a few angular degrees.

    There is at least one report somewhere in PriusChat archives of a shop that does rebuild EMPS. It may have been in Pennsylvania.

    Apparently you also have a 2007. It has Hall-Effect guts instead of resistive wipers, and will not fail in this way. It was never clear to me whether the 2003 had a system redesign, so there is a possibility that the salvage route above could give you the same problem later.

    Please post your steps toward a resolution and in the meantime drive carefully. The first time my 2001 got the shakes, I was just as surprised as you :)
     
  3. SteveWlf

    SteveWlf Old-on-Hold

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    Thanks fo the information. I'll be looking around or a replacement and study my manual on the location and replacement procedures.

    Steve
     
  4. SteveWlf

    SteveWlf Old-on-Hold

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    I just found the system discription and block diagram in the electrical section of the Toyota manual. I from what I gather, the only Electrical, of this otherwise mechanical system is the Torque Sensor and the Electric assist motor. All in the steering assembly.
    In other words, look around on ebay or salvage yards for that complete assembly. On the Gen1 that goes for about $115-150. (The computers are about 50 bucks if it should be that.) Both being from used vehicules of unknown service/condition, We Takes Our Chances.
    Removal of this is difficult but do-able (from under the car. Ahh!).
    Steve
     
  5. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Hi Steve,
    Check for chapman's posting but in addition to salvage, there are other options:
    • Toyota steering nut recall - a safety recall, Toyota sent owners of record a letter about replacing a failed steering nut. My understanding in some cases the assembly is replaced. Search should find the details. Your description of a hard turn is consistent with what was described in the letter.
    • Experimental - we have seen steering jitters in the past associated with torque sensors getting "noisy." Some data suggests it may be possible to burn-out 'tin whiskers' but this has not been tested. The steering ECU is located behind the glove compartment so the wires are easy to reach. However, 'one time' is an intermittent, we would really like to know it has come back and is NOT the steering nut recall.
    GOOD LUCK!
    Bob Wilson
     
  6. SteveWlf

    SteveWlf Old-on-Hold

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    Bob, isn't the torque sensor going to be in the mechanical assembly, possibly in the steering unit before the electric assemble.. It appears there is mechanicals between the steering wheel and the steering rack for safety. as in any power steering system. It would seem to me the torque sensor would be in that train of shafts and gears otherwise how could it measure torgue?
    Sorry, I tend to Think-Out-Loud when a think I should "counter a point". No Flame intended. Still need this group and the highly regard contributors/moderators.

    Steve
     
  7. tochatihu

    tochatihu Senior Member

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    Along the mechanical line, there is a rubber (flexible, elastic) plate. If the steered wheels are at a different angle than the steering wheel (in your hands), that plate deflects. The deflection is measured by the potentiometers.

    They comprise 'position sensors' but with the rubber plant in line, they become 'torque sensors'. From that information, the ECU tells the electric assist motor (downstream of the rubber plate) how much to turn and in which direction. To null the torque, equivalent to the angular difference through the rubber plate.

    This is how it works on good days. On bad days, noise from the pots is interpreted by the ECU as a good reason to start the shakes. Or as a reason to take the EMPS off line, which Steve hasn't reported yet.

    If destroying tin whiskers with an external voltage pulse is effective, I see no big reason not to attempt it here. Another possible patch that has been discussed is to filter the output of the pots, so that the ECU never sees millisecond scale variations.

    I witnessed a (destructive) teardown of EMPS once, at a Toyota shop. Sadly, no photos. But the potentiometers are quite well buried. Neither of us could think of a way to get to it without damage. If a fellow could do that, then several repair options could open up. You will see the pot signals pass through a ribbon cable wrapped many times around the steering 'hard shaft'.

    Anyway, I am interested to see all progress on this issue, because there are still a goodly number of NHW11s on the road. Maybe, some of those will never get the shakes, but a lot will. When the supply of new parts dries up, options for the fleet will be repair, salvage parts, or drivers with strong arms.
     
  8. SteveWlf

    SteveWlf Old-on-Hold

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    Had another cold morning and backed out of the car port in the same manner as before and had no problem or shakes. I'm gonna continue to operate as-is for now and see if it recurrs again. Then I will start watching for a slavage rach assembly. But who know if these salvage ones have the same problem, only time will tell Plus $150+.

    Steve
     
  9. bwilson4web

    bwilson4web BMW i3 and Model 3

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    You've got a good plan for this intermittent problem. If it returns and becomes somewhat reproducible, testing the tin whisker hypothesis could also save a lot of grief.

    You might also look at the schematics to pull the fuse feeding the steering ECU. This converts the car to manual steering mode for safer operation . . . IF the shakes get to be a safety issue. There will be an error light but the car should work fine.

    GOOD LUCK!
    Bob Wilson
     
  10. Avi's Advanced Automotive

    Avi's Advanced Automotive Independent hybrid repair shop

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    If I remember correctly, the warranty was extended through 2012. Does anyone have a copy of the letter we got when the nut replacement campaign started?
     
  11. ChapmanF

    ChapmanF Senior Member

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    Yes, I have the letter I got - it was a separate letter that came in the same envelope with my notice of the pinion-nut recall. It applies only to steering that is showing the sensor-caused shudder problem, and it covers replacement of the steering rack assembly (plus the miscellaneous bolts and pins needed to do that replacement). The letter says the coverage extends through December 2013 (yes, 2013) with no limitation on mileage.

    Toyota honored it in my case without any hassle, and my car got a new steering rack this Fall at 194000 miles.

    So I would certainly recommend that anyone experiencing this exact problem before the end of December 2013 talk to the dealer first, before looking at other improvised solutions.

    I think the MSRP of the rack assembly is now north of $2,000. The price went up (nearly double) shortly before the warranty letter went out ... my suspicion was Toyota wanted to make sure to keep enough parts in stock to cover the warranty extension they were about to make.

    -Chap
     
  12. Avi's Advanced Automotive

    Avi's Advanced Automotive Independent hybrid repair shop

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    I thought it was 2013 but wasn't 100% sure and didn't want to give out bad information. I would imagine the OP can get his taken care of under warranty.
     
  13. joedirte

    joedirte Member

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    So I have noticed a tiny steering shudder noise if the car is in READY for long periods of time. There is a slight mechanical vibration and clicking from the steering wheel, like it is trying to barely move wheel left then right. I'm pretty sure it is related to common problem, but goes away if you move steering wheel or normal driving conditions.

    Anyone else experience this, or I am just hypersensitive noticing what could eventually be failing steering motor?
     
  14. ChapmanF

    ChapmanF Senior Member

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    The complete thread on my experience starts with the mild symptoms I was noticing as early as 2008, and follows them up to the replacement of my rack in 2012. It might start off with a subtle effect that you feel through the wheel (reminiscent of a Macintosh telling you your password is wrong). You definitely have it if the steering wheel ever shakes like a wet dog when your hands are off. Torque sensor trouble codes from the steering ECU are confirmation. You can measure torque sensor signals. I used a chart recording of the sensor signals during a wet-dog shake to establish what the problem was, but catching a wet-dog shake on video would surely be enough.

    -Chap
     
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  15. joedirte

    joedirte Member

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    Thanks, I was aware of the wet dog shake, but I hadn't seen other reports of "haptic feedback" type concerns.

    I find it interesting it mostly appears to only do it when in READY for long periods of not moving the wheel.
     
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