A check engine light code is a code pulled from an on-board diagnostics scanner that determines the source of the problem in a vehicle. A local auto part store, auto repair shop or resources online can help locate the problem from the code.
Engine-Codes.com and OBD-Codes.com provide search functions for check engine codes. Both of these websites also provide symptoms, causes and possible solutions for the selected code, which are defined by vehicle.
An example of a code is P1300 on a Honda-made vehicle, which signals a multiple misfire. The most common repair for this problem would be to check, re-seat or possibly replace the vehicle's current spark plugs or wiring.