How do you reset a 2006 scion Tc oil change light?

To reset your maintenance reminder system (even if the light hasn't come on yet), you'll need to turn your key to on (but don't start!) and make sure your odometer is on TRIP A. Then key off. Press and hold the Odometer/Trip button. While holding down on the button, key the ignition to on (Don't start the engine!) The display panel will count down from "------" to "-"Continue pressing the button until the Trip A is displayed. After this step, you are done.

This answer is close but not exactly right. The odometer needs to be on your main odometer, not the trip odometer. Then it works just as stated above.