How do i reset the 2004 Hyundai Elantra check engine light?

The check engine light on Your 2004 Hyundai Elantra will usually shut itself off if the issue or code that caused it to turn on is fixed. For example, if the cause of Your check engine light coming on was a loose gas cap, if it's tightened, the light will turn itself off. Likewise, if Your catalytic converter is going functional, and You did a lot of stop-and-go driving, that may have turned on the check engine light due to the high usage of the converter. In most cases, Your Hyundai Elantra light will go off after about 20-40 miles. If You drive over that amount and the light is still on, You will need to bring it into Your mechanic, or Your local auto parts store so the light and code can be double-checked and reset.