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Discussion Starter #1
So I think the VSC system on my mother's 2005 Rav4 has lost its mind :serious

As I'm driving it on a twisty road it will suddenly and without warning SLAM ON THE BRAKES, and on several occasions this has caused the vehicle to lurch over towards the oncoming lane. The little "slip indicator light" comes on and it beeps as this is happening, and sometimes it will light and beep without the braking.

But the thing is: the road is COMPLETELY DRY when this happens. There is NO slipping occurring whatsoever. Yes, it's a twisty mountain road, but I'm not using excessive speed, and again: IT ISN'T WET AT ALL.

And there seems to be no consistency as to when this happens. It's usually on a corner, but unrelated to how tight the corner is, or even the speed at which the corner is taken.

Besides having the vehicle towed to the nearest dealership, anybody have any ideas?
 

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Dirty or intermittent ABS sensors on the wheels?
Any error codes via Techstream or OBD dongle?
 

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Discussion Starter #3
Dirty or intermittent ABS sensors on the wheels?
Any error codes via Techstream or OBD dongle?
I don't have that technology at the moment, but she tells the 120,000 mile service was JUST completed at the dealership .... like, ten days ago. I can't imagine that if there had been any faults they would have missed it. And this problem was actually occurring six months ago.

The thing is, it doesn't happen when my mother drives the vehicle. She lives on the flats and drives like an old lady (because she is :D) but when she comes to visit me in the mountains she usually lets me drive ... and THAT is when it happens. I'm sure I drive her car generally faster and more aggressively than she does, but I'm still basically within the speed limit. I'm just saying I drive faster as compared to how an old lady drives :serious...
 

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Don't assume that when you take your car in for a service they will automatically scan it for faults unless you tell them there is a fault or the CEL comes on.
 

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Don't assume that when you take your car in for a service they will automatically scan it for faults unless you tell them there is a fault or the CEL comes on.
Really? That surprises me. :serious I guess it's time to take it back to the dealership.

But I'm still confused. What is the VSC system supposed to do when it's working properly? Under what legitimate conditions would the vehicle decide it's appropriate to automatically apply the brakes ... hard?
 

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VSC works wonders to stabilize the vehicle.
For example, in the snow, I take hard turns on purpose just so that I feel the rear brakes being applied one wheel as it prevents me from fishtailing! It works wonderfully for me. It applies the brakes for a split second so that I can continue my course as intended.
 

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Discussion Starter #7
VSC works wonders to stabilize the vehicle.
For example, in the snow, I take hard turns on purpose just so that I feel the rear brakes being applied one wheel as it prevents me from fishtailing! It works wonderfully for me. It applies the brakes for a split second so that I can continue my course as intended.
I see. Does the slip indicator light come on when this happens?
 

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But I'm still confused. What is the VSC system supposed to do when it's working properly? Under what legitimate conditions would the vehicle decide it's appropriate to automatically apply the brakes
The VSC makes use of a steering angle sensor to determine how far the driver has turned the steering wheel. It also makes use of a yaw sensor to determine how fast the car is rotating, and in what direction.

So for example if you are driving under slippery conditions, and you approach a curve to the left, you would turn the wheel to the left by the amount appropriate for the amount of curvature. The steering angle sensor will notify the VSC processor that the driver wants to go left, and the processor will also expect the yaw sensor to indicate that the vehicle is indeed turning left at the same rate indicated by the steering wheel.

If you RAV should fail to turn left, or possibly over-steers (i.e.turns left more than the amount you turned the steering wheel), the VSC processor will sense that the RAV is not going where the driver pointed it, in other words the RAV is "out of control". It will apply the brakes on whatever wheels it determines necessary to correct the loss of control.

BTW, if the sliding car icon lights without beeping, it indicates traction control is being applied. If it also beeps, as in your case, it indicates that VSC is being activated.

You may have a faulting steering angle sensor, yaw sensor, or possibly faulty wheel sensors. This is unlikely though because a fault in any of these sensors would show up as a warning light. It is also unlikely you have a faulty component because the RAV works normally for everyone else.

Like Vanib says, the VSC works extremely well, way better than I have experienced with any other car equipped with VSC. You may have something as simple as a low tire pressure which causes a little slippage with your more aggressive driving style.
 

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Discussion Starter #10
You may have something as simple as a low tire pressure which causes a little slippage with your more aggressive driving style.
Thank you for that detailed explanation. I feel I understand the system much better now. That being the case, I still believe that there is something wrong ... perhaps the tire pressure or a bad sensor, though like you say, a bad sensor should be indicated.

My "more aggressive" driving style really is just in comparison to how my 71 year-old mother drives. More accurately, my style of driving is much closer to "normal" than hers. And that fact that doesn't happen consistently makes me think something is awry. :serious

I guess we are dealership-bound
 

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Yeah, definitely get it checked. Be advised the VSC will work in dry conditions as needed, but it shouldn't cause you to screech to a halt. As Vanib and Rickl allude, the tires could be the culprit. I'm thinking poor tread or low inflation on front tires.

When I practiced (on snow), I noticed a front wheel skid would make the steering wheel play very "heavy" to keep the driver from over-correcting and there was some braking. In dry conditions, this would be the same as someone drifting onto the right shoulder of a road, then instinctively cranking the wheel to get back on the road--and inducing a rollover. But the VSC keeps the driver from doing that. Perhaps in your mountain curves, you were getting some front wheel skid.

On the other hand, if it was a rear wheel skid, the steering play would be super "light" so the the driver could immediately point the front of the car in the direction of the skid, and no discernible braking. It's a pretty amazing system.
 

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It's a pretty amazing system.
Yes, everyone on this forum seems to have nothing but good things to say about it. This also leads me to believe something must be wrong.

According to my mother, she had the tires check just prior to coming out to visit. But she did have them checked in Phoenix where she lives, and said the guys might have put the pressure a little low on purpose because they were checked hot, and it's REALLY hot there right now.

I'm going to check them. I know I'll get a variety of answers to this, but with the VSC system in specifically in mind, what are thoughts on tire pressure? And they are cold right now.
 

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Not sure what your gen 4.2 says, but if tires are cold, you usually can't go wrong with what the placard on the inner door sill reccommends. Mines says 32-lbs, but I bump it up to 34 for a little less rolling resistance and to allow for some cold nights. I can see folks in Phoenix playing a lot of tire pressure games during extreme heat variations--and maybe getting too low--or too high.

Just for grins, check your tread depth: use a penny, insert in each of the tire grooves. If Lincoln's head is deep enough to 'get a haircut,' you have enough tread...
 

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But thread is more for snow/rain. It is to prevent hydroplaning.
F1 formula car tires have no tread so as to maximize surface contact.

That's why those tires are swapped out for tires with treads only when it rains.
 

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Hmm, somehow I think the 'stickier'compounds on racing tires might differ from street tires, besides being much wider. But given your theory, the worst case scenario would be overinflation with minimally treaded tires causing a crown with little surface contact. In any case, best to make sure they are street legal and properly inflated so as not causing a skidding problem.
 

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This is becoming a common problem as our RAV4 get up there in age. I wonder if it's related to worn bushings or electronics flaking out.
 

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I'm having a similar problem. Wondering what you found out at the dealership. I'm thinking the yaw rate sensor is sticking. My front brakes get a small amount of pressure applied when it happens and they heat up "red hot"
 

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Besides having the vehicle towed to the nearest dealership, anybody have any ideas?

It definitely should be checked out, but till then if it worries you, and especially on Dry pavement, maybe you can disable it, my 4.3 rav has buttons on the dash to do that, check your manual.
Ott.
 

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Ott. and expeditionfree, the OP's last post was from over a year ago and like in many other cases we never heard any resolution.

expeditionfree, restating your specific issue might get you an answer.
 
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