If your around a Autozone they will plug a handheld tester in for you and tell you what code your car is spitting out. They helped me out big time! I have had to check codes a dozen times. They had no problem at all helping me out.
The easiest way is to stop by your Toyota service center and ask for the manager. See if he'll take 45 seconds and hook up their diagnostic monitor to the terminal under your steering wheel and tell you the codes and what they mean. Otherwise, go to mkiv.com and follow the instructions. Under the hood near the firewall on the passenger side is a little black box with a flip-up lid. You basically bridge two of the terminals together and count the "check engine" light in the dash as it blinks. For an error code of 21 it will blink twice, then pause, then blink once.
on an obdii you cant pull the codes with out a scan tool or a harness that hooks to your laptop with software. YOu also cant reset it. Need the tool. Computer will clear code if the item causing it was corrected. .