Interesting warning light -Video attached

Are all four tires the same type, size, and relative age?

 

When you say slightly different, exactly what is the difference? Age, size, brand etc. Also do the tires on the front match each other and do the back ones match each other.

There are posts here on PC that discuss this issue. Generally what is found is that tires are mixed which causes the computer to think that one tire is rotating faster or slower than the others hence causing the skid alarm.

With all that said, please specify what the slight difference is.

 

Looked at your history of posts here on the forum.

Are you having the same symptom that you referred to in this string?

Traction control light stays on when it rains... | PriusChat

If so, I would have the speed sensors checked. You might have a problem there. As discussed earlier and in the other thread the system works by counting revolutions of the tires.

You mentioned in your previous post that four tires were new Michelins. Has there been a change since then in the tires?

 

Thanks for the additional information. Now I understand. Chances are that the two different tires have enough difference in the actual RPM of the tires to cause the skid control light to come on. This is a common problem with the Prius when tires are mixed or mismatched.

FWIW, just about everyone has this problem when they put the donut spare on. Same thing is happening. The revolutions of the tires are not the same, so the system thinks one of the tires is spinning and causes the light to come on.

If you want to solve the problem I would suggest you investigate the RPM of both tires and try to find a couple of tires that match the RPM's better. A full new set of tires should solve the problem, but it is also a large expense especially if the tires are relatively new.

 

I may be wrong, but I believe all four wheels have sensors on them. My understanding is that when the system sense the RPM difference it will apply braking pressure to correct the problem since it thinks a tire is spinning faster than others.

Try to find a couple of tires that will match the newest tires you have. Make sure they are the same brand, size, and type including load range. Once you do that, I think the problem you are experiencing should go away.

Refer to Toyota Safety | Traction Control, Brake Systems & More - the page says that the computer monitors all four wheels. See section on abs and also vsc on that page.

 

The 185s go 76.87" per revolution, the 195s go 78.48" per revolution if my math is right. So the smaller tire has to spin faster to "keep up" with the larger. When the stabilization control sees tires spinning at different rates, it assumes something bad is happening.

I bet making all the tires the same size will fix the problem. You could buy two to match the better pair of what you have if money is an issue.