Stop in for a cup of coffee

I've had my 08 Caddy DTS for almost 4 years now. Yesterday check engine light came on. Need to check that today....
I know a guy in your area that works on cars...
Thanks to owning newer Mopars, I don't even own a scan tool. All my recent vehicles had self diagnostics. Just looked up the codes online. No clue what I need for Mazda, but that's the dealers problem for a couple more years.