There are various methods Frankie, cheapest is an Elm327 device your smart phone and an app. Or you can go down either the Cardiff or peak instruments route. All will give you the codes, but the more sophisticated will give you some idea as to the actual fault, as a code only really tells you which sensor picked it up, but in most cases you get more than one related code so you can Sherlock Holmes the answer.
I have the Elm337 (wifi version) with my my Ipad, and an App called EBOD- Facile, cost £15 all together, works well on all my cars, plus you can datalog.
Hope this helps