Buy this
http://www.ebay.com/itm/Auto-ELM327-...item35c399c8f2
and then buy Torque (theres a free version but the pro version is worth the $5) on your smart phone. Connects through bluetooth and you can read/clear codes, check your cars diagnostics as its running, do 0-60 times, 1/4 mile times, 1/8 mile times, read your HP (not sure how accurate it is)
but for the 15 bucks its def worth it.