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Vehicles 1996 and newer have an OBD-II port that can be used to read/reset Check Engine Light (CEL) codes and various sensor readings. The port is usually under the dash.
OBD-II scanners have gotten progressively cheaper and are now available in bluetooth/wifi models that communicate with and display on your smartphone and tablet. They are generally less than $20.
Once you have the CEL code you can google it or check it against published lists of codes for your vehicle's make: