2005 Chevrolet Avalanche check engine light

The check engine light on my 2005 Avalanche came on today. The vehicle still has less than 40k miles. The manual says that an opened gas cap can cause it. I checked the cap and sure enough the cap was unscrewed and just resting in the gas tank filler spout. I reinstalled it and checked out other things. Oil level and quality-OK; Oil pressure-OK; Temperature-OK. No other problems are evident. check engine light is still on. Questions: Is there a re-set procedure to get the check engine light to go out? Are there any other things I can check or do?

If the problem has been fixed, the check engine light will go out in a few “trips”.