Check Engine Lite is on on 2002 GMC Sonoma

What are the possible problems associated with the illumination of the Check Engine Lite.

Asked by for the 2002 GMC Sonoma
Check out these articles in the RepairPal Encyclopedia;
http://repairpal.com/check-engine-light
http://repairpal.com/check-engine-light-diagnostic-assistant
2 more answers , 1 more comment
Go to a Advance or Autozone parts house and ask them to code out the computer. Ask for the code numbers. e-mail me at swaths3644@mypacks.net
Can't help without a TROUBLE CODE
02 sensor front of catalytic converter or rear of converter.