Why does a loose gas cap turn on the check engine light?

Simple question, pretty neat answer!
LINKS TO SOME GOOD MERCH:
https://good.store/collections/technology-connections
https://good.store/collections/awesome-socks-and-undies-main

other links 'n stuff:
Technology Connections on Bluesky:
https://bsky.app/profile/techconnectify.bsky.social

Technology Connections on Mastodon:
https://mas.to/@TechConnectify

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