Check Engine Light On 2003 Gmc Yukon How Do I Get The Check Engine Light To Come Back On?

How do I get the check engine light to come back on? - check engine light on 2003 gmc yukon

MY 2003 GMC Yukon XL Denali check engine yesterday, and I took her into the store to get scanned. They said it was the trigger, and restore engine light control. I bought the car two days ago and want to meet again to fix for free, but I can not back off. Is there a way to verify that engine to make? Thank you!