You will need to jump pin 1 and 4 on the diagnostic connector to enter blink mode. Then with key on and engine off the check engine light will blink the code. Most likely the O2 Sensor is faulty or fuel is rich or lean. Most of the time this is the issue with these trucks.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.