check to make sure both the gas and oil cap are straight and tightened. Fill the gas tank if you find the gas cap was loose to build up pressure and that usually resets the check engine light to off. http://wiki.answers.com/Q/How_do_you_turn_off_the_Oxygen_sensor_light_and_the_check_engine_light&updated=1&waNoAnsSet=2
Buy a kit at Wal-mART OR AUTO PARTS COMES WITH INSTRUCTIONS
Check your fluid levels.
The check engine light comes on at start up for a bulb check. If it stays on with the engine running the computer has detected a malfunction. You need to have it checked for codes.
The check engine light (service engine soon) comes on and stays on when a problem is detected by the self diagnosis system of your vehicle.
The check gauges light comes on when one of the gauges is not in the safe range.
You can buy the check engine computer and the book comes with it. I know, I bought one. When your check engine light comes on, you plug it in and check the engine and it will give you the code and you look in the book for that code and it gives you the answer.
it comes on when you need gas
check for a bad door switch.
If you look at the air filter box, you will see the air intake hose that goes to the engine. As soon as it comes out of the box, it will be in that hose.
The 1/2 tons used the 4L60E and the 3/4 tons used the 4L80E.
check the brake fluid reservoir and add fluid if necessary.
check coolant sensor float most common problem.