Traction control light comes on-slows car down to 20 MPH, Fix?

It would seem to me maybe you need to at least check both of the front wheel sensor wiring making sure they're all plugged up clean I think if you use an ohmmeter and you pick up the given side and turn the wheel You should be able to count the beats on your multimeter according to the amount of cut outs passed by the sensor . Or something similar to that seems to me the car is being told to put that on the traction control that is because it's not seeing something which is why you don't have a code. Or it's really seeing something and activating traction control completely and doesn't need to I've never seen that happen on one of these every time I see traction control I'm losing traction and can feel it right underneath my car with me in it so for it to be activating and nothing going on sounds like some sensor is not being sensed or not even plugged up or in the mix at all.

 

If you don't have it, try to get TechStream, You can monitor each wheel speed sensor to see what they are showing for detected MPH.
It may not be the one you think.

 

Get Techstream or one of the capable scantools in this thread.
https://priuschat.com/index.php?posts/3290690

Several can access ABS system data to view wheel speed sensors.

Might be one tire might have different size. Might be cracked tone ring on the LF axle. Sometimes the WSS mount is off some (corrosion under sensor or damaged screw)- but usually that causes "false" ABS activation on braking.

Posted via the PriusChat mobile app.

 

I am pretty sure the skid ECU has a "check mode" that the repair manual suggests using after hubs have been changed and so on. In the check mode, you drive around a little bit in a certain pattern, and the ECU looks at all of its sensor signals and holds them to a much stricter standard than it normally does, so it's very likely to flag any issues that might be missed or intermittent in normal operation, and if the whole check mode routine passes, that's a pretty good indication of health.

At least, I know Gen 1 had such a check mode and Gen 3 does, so I'm guessing Gen 2 does also, but I don't have that repair manual in front of me at the moment.

 

It'll be in the Repair Manual:

Toyota Service Information and Where To Find It | PriusChat

In the Gen 3 manual, for example, the heading is really SENSOR CHECK USING TEST MODE, and can be entered with a jumper from TS to ground, and it starts the brake warning lights blinking, and then you do nothing for a second, then stomp the brake for 3 seconds, then drive over 28 MPH for several seconds till a light goes out, then stop till a light blinks, then drive in a U turn at about 3 MPH, then stop and park, and a buzzer sounds for 3 seconds if everything went right. You will then have tested all the wheel speed sensors, the acceleration sensor, the master cylinder pressure sensor, and the yaw rate sensor.

But the procedure in my old Gen 1 was different, and I'm sure the details are different in Gen 2 also. As you can see, you kind of need to be looking in the right repair manual for your model to know the right sequence of things.