If you disconnect the VSC gyroscopic yaw rate sensor (it is located under one of the front seats and mounted to the floor, pull the plug) the system will not function, but it will also permanently turn on the VSC light. I don't think that this will affect the ABS or traction control systems, but I could be wrong. If the problem is in the VSC computer itself, this may not solve your problem.

 

Very nice response. I will give it a try. I called Toyota regional today, and it does not appear that this is a systemic problem with these cars, just mine. It will be virtually impossible to chase down the exact cause since it is so intermittent, so they don't really have much else to offer other than to replace lots of parts and guess. I will call to see if removing this sensor disables the ABS. If it does not, then that is the answer. If they won't tell me or don't know, then I can certainly unplug it, and get on a gravel road, come to a panic stop, and see if the ABS kicks in under safe conditions.

 

Don't count on anybody at Toyota or with a Toyota dealer to give you an honest answer. There would be a potential liability issue if they did.
The best way would be to test the ABS and traction control systems yourself, as you suggested. A wet parking lot should do the trick.
Also, after you disconnect the yaw rate sensor, if the VSC still activates like before, this would be a dead giveaway that the VSC computer itself is probably faulty.

 

So, I called Toyota service, and they told me that if I disconnect the sensor, the ABS and Traction control are also disabled. Not good. So, I will have to test it myself. Dang!

 

I could have predicted that they would tell you that! What else would you expect them to tell you?
To the computer, disconnecting the yaw rate sensor would have the same affect as if it were defective. I can't imagine that a defective yaw rate sensor would cause the ABS not to work (maybe the traction control, but not the ABS), but again, I could be wrong.
You need to test it yourself.

 

I know what you mean. Still, the guy seemed genuine. Despite that, I intend to test myself since it is easy to do so.

 

You will know whether or not the ABS and traction control are working by the lights on the dash. If you disconnect the VSC and the ABS and Traction dash lights remain unlit after starting the van then you should be ok. If the lights come on then you will know immediately that they are disabled.

 

Hopefully I can try it this weekend. I will report back with the results. Good thoughts.

 

My Sienna did this one time a few years ago. There is a TSB BR004-03 which addresses the VSC and points to the Yaw Rate sensor.
Stan

 

OK, anybody know where this sensor is located? I looked under the driver seat, and disconnected 3 different harnesses. None of them disabled the VSC. So, I don't know where the sensor is...

 

To start, here is the TSB list for the 04 Sienna that refer to "yaw rate" since there are 131 in the full list.

1. BR004-03: 04 Sienna: DTC C1234 - Yaw Rate Sensor (Revised)
2. T-SB-0288-08 Rev1: '04-'10 Applicable Toyota Models: Front Seat Squeak Noise
3. BR001-04: Zero Point Calibration: 04-05 Models with VSC (Revised)
4. T-SB-0020-08: Disconnect Battery & Perform Zero Point Calibration After Wheel Alignment Adjustment
5. T-SB-0077-08 Rev1: 04-08 Sienna: Mobility Converted Vehicle Service Information
6. SS006-07: 01-08 Toyota: Absorbed Glass Mat (AGM) Battery Information
7. EG014-05: All Toyota & Scion Models: Radiator Cap Inspection
8. PG017-02: Battery Maintenance for In-Stock Vehicles & Pre-Delivery: All Models & Model Years (Except Prius)(Obsolete)
9. TC007-03: 04 Sienna: ECM Calibration: Shift Feeling Enhancement (Revised)
10. EG055-06: 04-06 Sienna: Engine "Pinging" or "Knocking" Noise (Revised)

Note that BR004-03, BR001-04, and T-SB-0020-08 all pertain to the yaw rate sensor. Basically, the sensor needs to be rezeroed after each alignment or steering part replacement. I have attached all three so you can read through them. The sensor is mounted on the floor under the front passenger seat.

The Skid Control ECU does the VSC and TRAC functions. I added an excerpt of the New Car Features document that explains how things operate. Unplugging the Yaw Rate Sensor disables one input to the Skid Control ECU and may affect TRAC as well as VSC. It may not be the problem as well. VSC is so embedded in the braking system, I would not try to disable it. It may get fixed just by disconnecting and reconnecting things.

I take it that the dealer reported no codes?

 

I appreciate your thorough response! Looks like disabling the sensor is not the way to go.

I have brought the vehicle in numerous times over the last 3 years or so for this intermittent problem. They just can't figure it out, because it is so intermittent. But it really renders the car unsafe. I think I would be forced to replace parts 1 by 1, including perhaps the whole front end and steering rack before chasing this down. Just not worth it. I think the problem is somewhat unique to my car, as searching various forums does not seem to trigger much history of this in other cars.

 

... Note that BR004-03, BR001-04, and T-SB-0020-08 all pertain to the yaw rate sensor. Basically, the sensor needs to be rezeroed after each alignment or steering part replacement. I have attached all three so you can read through them. The sensor is mounted on the floor under the front passenger seat. ...

It would seem that as the steering gets knocked out of alignment it could also cause VSC issues then, true?
Stan

 

I know this is an old thread but any update on this? I'm experiencing this right now

 

I have a canadian 2005 CE FWD and it doesn't have the yaw sensor or Trac/VSC. I do have ABS brakes though and would suspect that the control computers are the same as the ones you have, but with those systems turned off. Not sure if a dealer would be willing to make that change for you though.

 

As of right now, dealer cant find anything- Any recommendations?

 

I am experiencing this as well - anybody?

 

I just had this happen to me three times this weekend on my 2005 sienna.

 

I have just purchased a 2005 Sienna XLE that is now having the same problems. We have just replaced the Skid Control ECU, which eliminated all codes but did not fix the problem. The wheels lock up intermittently when steering to the right through a curved entrance ramp. We are looking at replacing the Yaw Rate Sensor and/or Steering Angle Sensor next, but these are Hail Mary actions. Does anyone have any ideas or solutions?

 

Before replacing all that I would check that the cables to the wheel speed sensors are not damaged, especially the one that is stretched when turning. The VSC needs wheel speed to function.

 

I'm having the same issues on my 2004 Sienna. the VSC comes on when turning right on a ramp even at low speeds <30MPH. Just had a frustrating session with the service dept at the dealership where they tried telling me this is "normal operation" for the VSC. Since they didn't read any codes they understand the yaw sensors and everything else is working normally. Has anyone been able to fix this issue? if so, how?

 

I'm experiencing this as well. My rear brakes will apply themselves as I leave a stop sign and power is cut. Additionally, I will sometimes get the Stability Control light and beep as well. This started after the front wheel bearing was replaced on my van. A rear wheel sensor code came up originally but now can't get any codes to show after replacement of that sensor.

 

I performed tsb Br001-04, zero point calibration and now both the VSC and track lights off are on. I will have to drive it some more to see if its permanent or temporary until it learns.

 

Hello Techi, I know that this is an old post, but I see that you recently added to the thread. I recently replaced the whole Rack-n-Pinon, somehow got the steering wheel misaligned after install. That was corrected during wheel alignment but I see that I have to do this zero point calibration. Wondering if you performed zero point calibration with or without diag tester...I don't have a diag tester and am wondering which method you used and if it turned out good.

 

I have 2008 Sienna FWD. On occasion have issue that VSC and Trak come on, causing some troubling handling issues. When it kicks in can be startling and scary, especially for wife. Eventually the lights come on steady and I breathe easy knowing it is temporarily deactivated. I am getting "zero point calibration" and alignment today. If still problem will replace "Yaw Rate Sensor" gamble it is culprit. After that I don't want to spend anymore money on it. I would be happy with it permanently off/disabled since we drive in Bay Area California with good road conditions. IS there a "go to" simple way to disable? when this thread in 2015 ended didn't seem like there was.