I recently purchased a 2002 Chrysler 300m. Does the same key open and start the car?

The car does have the remote, but the salesman put the key in the door to see it it worked, and later the check engine light was on within 15 min. That's why I am asking. I wondered if the key could have set the engine light on due to the electronics that are involved. He told me today it was just a vapor lock from the gas cap that cause the light to go on. Just trying to find more out. thank you for your info.

I have a 99 300m and there diff