Mechanics please help. Wife put diesel fuel in place of oil when doing oil change?

I left the Hummer with the wife today and she tried to impress me and change the oil at our trailer park. Well instead of putting engine oil in, she grabbed the container that had diesel fuel in it. I dont hear it knocking and oil pressure is good but the check engine light is now on. I had her take it to the professionals at autozone but they said the code was a glitch, so she was told to take the negative off the battery and it would clear the code. When she got back to our trailer community, she did that but the light is still on. What should we do?