Depends on which one you buy. Some just read/erase current codes which is fine if that's all you want it to do. Others can monitor all sensors while driving the car to see if something's off somewhere so you can figure out why codes are being thrown. Some can read pending codes. Some can do even more. It all comes down to what you want it to do and how much you can spend. Actron's 9135 is a good scanner because you can read/wipe code, see pending codes, monitor sensors (real time), and the display shows both the code ID numbers and it scrolls the wording below it so you don't have to look in any books or anything. I got one from AutoZone for $150 when it first came in, but they've since changed the price to $200 I think because they sold me mine for the older 9035 price. Diablo's Helion scanner is nice too, but I couldn't justify it's $600-650 price when it only did one or two more minor things I could find over the 9135.