Toyota Repair: ECU or ECM on a 2003 Toyota Sienna, toyota sienna, toyota dealership

Question
We have a 2003 Toyota Sienna and we just failed our emissions test - our check engine light was on. I took it to the Toyota dealership and the said our computer was shot and we would need to get a new one to the tune of $1500. So we purchased a used one for $100. Which leads me to my question....where is the ECM or ECU on a 2003 Toyota Sienna and how do you replace it? I need to have the emissions testing done again so we can renew our plates. Thanks for your time. Tina

Answer
I find it a little hard to believe that there is a problem with the ECM. It's located behind the glove box, remove the glove box. If for some reason replacing it doesn't fix the problem let me know.The reason I have doubts about this is that the ECM is the almost always the last thing to suspect for an engine light to be on, let me know if you need more help with this.