VSC / Steering problem?

Has anyone experienced something similar to this?

This morning I was navigating a curved exit ramp on a slight incline. The road was dry and I had total control over the vehicle. Without warning, just a few meters into the turn, my 2004 Prius' vehicle stability control or VSC came on for no apparent reason. Suddenly I found that I no longer had control over the vehicle and rather than continuing on the turn, I was heading straight for a guard rail. The car did not respond to the steering wheel so I hit the brake in order to avoid the guard rail. Braking caused the car to turn enough that I was able to go safely off the road but I could not actually stop the car. The car stopped when it finally hit a small baby tree. The VSC indicator remained on until I 'rebooted' the car. At this point the car seemed to operate fine.

The car is a 2004 Prius with just over 20,000 miles; routine maintenance has been done. We did experience the computer problem, and the recall work was done.

After researching this problem on the internet I found other Totyota VSC issues, including a similar user report about a Toyota 4Runner:
I took the 4Runner to the Toyota dealer, and they said that the computer code indicated that the yaw sensor had sensed a problem, so that activated the VSC system.... While accelerating up a dry, clean on-ramp to a highway, it recently pulled me off the road onto the shoulder because the front right brake applied and the engine throttled down. This almost caused a crash.

That person associated it with charging his phone in the car:
When I have my cell phone charging through the on-board power adapter (cigarette lighter-like socket) in the center console, and I bring the RPMs above 2500 or so, the VSC system malfunctions. Sometimes it just shuts off (the VSC and Track Off lights come on), and other times the VSC actually engages. When it engages, it applies the ABS to some of the wheels, and it reduces engine power. If the warning lights come on, turning off the ignition and restarting the engine clears the lights. When the VSC is actually engaging, yanking the charger out of the adapter immediately disengages the VSC behavior. This only happens when my phone is plugged in and charging. I've had a CD player plugged into the adapter and an XM satellite radio plugged in, but the problem didn't occur either of those times. Also, I've had the phone's charger cord plugged into the power adapter, but without the phone attached to the charger, and the problem also did not occur.

 

I continued to google "Toyota VSC Malfunctions" and found that there are problems with VSC reported across the product line. The general problem is that the VSC activates inappropriately, locking the brakes, decelerating the car, and basically steering the car into trouble. Here is a link I found this morning about a Sienna. In this case, one of the replies reported that tire pressure can cause this. IN MY CASE, my car was just in for the 20,000 mile maintenance, but this dealer has not checked tire pressure when rotating tires. In other words, I think the front tires were underinflated and the rear tires were two pounds higher than the front tires. The car is now at another dealer, so I cannot check.

Here is the link I found, but note that another driver responded that it happened to them too:

http://townhall-talk.edmunds.com/WebX?14@@.ef00024/2475
http://townhall-talk.edmunds.com/[email protected]@.ef00024/2485

Re: charging devices- it is likely my son was charging his phone when the incident occured, but I am thinking that is a red-herring. We do routinely use phone chargers, a Garmin GPS, and at times, an inverter for lap tops.

 

I am from Southeastern PA (Plymouth Meeting) and the weather was in the 50's and the road was dry. A state trooper arrived at the scene and volunteered to file a report to verify the road conditions. It is on file - no water, ice or skid marks.

It is being checked out, but can I trust the dealer? The comments on the web don't indicate concern from Toyota. It really does seem to span the product line.

 

Thanks to all. My goal had been to determine if others had experienced this also. I think I can report anecdotes from other Toyota owners, but not other prius owners at this time.

I will do NHTSA, depending on Toyota contact outcome. I am concerned that this is problem generically with VSC.

The dealer did not give me a warm and fuzzy feeling that they would get to the bottom - I suspect they will tell me only that the VSC was activated without accepting that it activated in error, on a 50 degree day, on a dry, clear road.

My local dealer (not the same one that has the car now) did the 20,000 mile maintenance just one week before - they can't claim the car was in ill repair, and it is still under warranty. And the Trooper's report validates the road conditions.

We shall see where it goes.

 

Okay - here is the update:
First, my son tells me it was the skid light that came on.

The dealer I took it too found no codes. At my insistence, they checked the tire pressure - it was at 30 pounds all around (Actually, my digital guage said 29 front).

Yes, I really paid $60 the week before for the 20,000 maintenance, in which the dealer documentation says the not only rotate tires, they check the pressure.

 

Multiple questions here.

The road is relatively new - completely rebuilt - no pot holes.

He did not hear the audible VSC alarm.

This is a ramp to the right, banked and uphill. The car went straight instead of turning right, and my son kept turning the wheel right.

He applied the brakes and the car spun around. Instead of going right, he wound up off the road on a patch of grass. A small tree actually stopped the car (denting the bumper). If he had not hit the brakes, he would have gone into the barrier. The brakes didn't slow the car - just changed the direction.

BTW - the tires should have been 35 front and 33 rear. While the dealer said it was 30 all around, I had measured the driver's side it before I went in to the shop - I measured it with a digital guage as 29 front, 28.5 rear.

For anyone familiar with the Philadelphia area, this happened on the west bound schuylkill expwy ramp for 202 south.