You did not mention at what speed it happens. I am hoping it's not happening at slow speeds, such as 10-15-20 km/hr (10-15 miles/hour) Only when the sensor notices slippage is when it activates the traction control. Now for the same curve, if you "disengage" the traction control (or turn it to off), do you still get the same observations? I am asking because, the traction control nanny does not completely give up the control to you. So when you turn it off, and don't get any artificial slowing, you are driving in what Toyota would call in an acceptable way.
Just wanted to ask, how long have you been observing this? Has the tire got to do anything with it? How's the tread? Are you certain tires are not slipping? Have you tried changing tires to verify? Have you tried in curves in multiple locations at multiple times of the day? I am asking because, sometime seemingly innocent curves are not so innocent all the time, given slippery surface materials sometimes, such as cobblestones. Also, do you carry load above the roof? Stability control systems are a tricky business.
Again, I am certain you checked off all these already, but just wanted to make sure it's not the car that's giving you grief.
There wouldn't be any error code, because the car is "doing its job". Now if they have any blackbox.... It seems the traction control is acting too sensitive. Has it always been like this?