2003 Silverado

I have a 2003 Chevy Silverado. It has 21,000 miles and I have had five (5) "Check Engine" light instances. The last (2) have been for an Oxygen sensor. The other three were for a gas tank sensor, an air emissions problem and a condenser problem. Does anyone know exactly what will cause a "Check Engine" light to be activated? Also, does anyone else have similar problems?

I have the same problem. I have 30,250 miles and my light has come on 3 times in the last 3 months. The first was quoted as a mass airflow sensor short, and they didn't do anything. 2 weeks later, same thing only this time I was stalling out at idle so they replaced the MAS. Now, a month later, I have the gas tank sensor error. They said that the tank isn't holding pressure, but they can't find the leak. Looks as though I will be taking the truck in every month to get something fixed at this rate.