can someone please tell me whats the difference between obd1 and obd 2

OBD2 has been in effect since MY96 of every car sold in the U.S. Search Wikipedia for more details.

 

Well, you model year is going to tell you which you have. The Prius, being make since 2000 will always have the OBD2 and the later Prius had OBD2 but with much of the data on the CAN bus not readable from some of the cheaper OBD2 readers. I have a fairly good/expensive OBD2 reader has worked on most all cars until I got into the Prius, Gen2. Worked to some extent on the Gen1 and gave me some of the P3xxx codes. However, on the will only read the non CAN bus code apperantly.
If you need a better discription of the CAN bus data format, I will leave that to someone else.
Steve

 

Wiki is a good place to start. Then search the vendor sites for chips that speak OBD. Their application notes will give you more details than you can image.

Bob Wilson

 

The difference is 1.

OBD 1 + 1 = OBD 2.

How would it grate?