Elley–The presence of the CEL is very important, so for future reference, you DO need to mention that detail when you ask for our opinions. Please find out whether it is on steadily or if it is flashing/blinking, as that distinction is extremely important.
If the light is on steadily, he can drive to an auto parts retailer, and have them check the trouble codes that have been stored. If the light is flashing/blinking, he needs to get the car to a competent mechanic right away, and not continue to drive it.