Believe it or not, I purchased my vehicle in November of 1999 and 2 months later, the Check Engine light came on and just refused to stay off. I took it back to the dealership where I purchased it ( a Toyota dealership in PG county) and they tried everything with it - but could not keep the light off for more than 5 minutes.
After 4 Toyota dealerships, 10 computer reprogrammings, and 4 years, I finally moved to Rockville and decided to give 355 Toyota a try. Sure enough, they fixed it and it has never come on after that.
The people their are nice and intimidation-free too. I highly recommend taking it to the dealership if you have a Toyota and live in Montgomery County.