There's more info available than just the 'stored in memory' codes that you can retrieve by jumping wires. Most domestic cars were OBDll compliant in '95, all had to be in '96. The main difference is the connector has to be identical on all vehicles (thank you!), adaptors for various cars could cost over $100 each before OBDll.
OBDll also requires that certain parameters be available with a generic scanner - 21 parameters, if I remember correctly. Most OEMs have many, many more available if you access them with
their approved scanner.
Aftermarket scanners (professional type) typically $1500- $2500. Add in annual updates, $500 - $1000 for imports and the same again for domestics. If you want to be able to 'flash' the EEPROMs to correct driveability flaws in the firmware that became problems after the cars were engineered and sold, add a bunch more for the ability and that much more for an annual subscription to each OEM's updates.
There's a lot more to this, but I see I've run away from the simple question again....
