what year is your sienna?
if you have the light come on but not stay on then it's an intermittent problem and sets a soft code.
what you should have done is hook up a scanner and watch the data stream when you can recreate the symptom. this way you can see what may be activating the light. Or scan the ABS when the light is on. Cycling the key will reset the ABS and if it doesn't see the condition it will turn off the light until it happens again.