Worth noting since we're all supposed to be hackers, the connector hasn't changed over the years since '96 OBD II in the US, but there are several protocols and many vendor-specific subsets of interaction. Early "code readers" may not work on later cars despite having the same plug because the underlying protocol is different. It's easy enough to find out what the protocols are on wikipedia if you're interested. What's available greatly depends on the specific vehicle manufacturer but there is a minimum set of data including DTC's (diagnostic trouble codes) for all.
With manufacturer-specific details, there's an unbelievable amount of data and even commands and firmware download capability through that port. A decent PC-based system with specifics for your vehicle added-on is a worthy tool if you tend to do your own car repairs. Or at least you can go into the shop and tell them what part you need and know whether you're being quoted a reasonable price.
With manufacturer-specific details, there's an unbelievable amount of data and even commands and firmware download capability through that port. A decent PC-based system with specifics for your vehicle added-on is a worthy tool if you tend to do your own car repairs. Or at least you can go into the shop and tell them what part you need and know whether you're being quoted a reasonable price.