cheap OB2 scanners??

Inexpensive code readers are just that. They will read codes and clear codes. as the price goes up so does the features. Some have a code library that tells you what the code means. Some others have data stream. Some do ABS and airbag. The next step up does transmission. The expensive ones will do it all and then some. Remember the cheapies only do OBD2 (1996 and newer) generic codes (common codes that the manufacturers share) "Manufacture Specific Codes" can only be accessed with a deluxe scan tool and not a code reader.
Pre OBD2 cars (96 and older) need a different software package and manufacturer specific cables to work. tmm