What is the difference between OBD-1 and OBD-2 and is there such a thing as OBD3?

obd1 is 95 and older and obd2 is 96 and newer. altough some early and mid 90's vehicles were obd2 compatible. there is talk to obd3. Its almost like big brother for vehicles. Your vehicle will transmit a signal if your vehicle has an emmissions fault. a transponder(built into a stop sign or stop light for example) picks up the signal and your are then later sent a notice. Its all just talk for now. But im sure theres much more to it. the difference between the two is SAE got involved and set a standard to on board diagnostics (OBD). for example a code p0300 is : random misfire. P0300 is the same for a toyota honda chevy ford chysler etc. A P0xxx code is the same for all OBD2 vehicles no matter what make and model. But a P1xxx is a manufacturer specific code for a more indepth code for more accurt diagnostics. Also on obd2 vehicles the diagnostic data link was required to be located under the dash driver side dash board. obd1 it could be located anywhere on the vehicle. OBD2 also has the added feature of real-time data and freeze frame data.