If your looking for info on VPW obd2 check out this guys site!!
I have loaded his code in an atmega8 and 16's and it runs just fine.. I rewrote it for 16Mhz and also for the internal 8Mhz..
Both worked great tied serially to a computer and I was lazy and simply added another atmega8 next to it and shared the crystal.. tied the serial lines together and wrote some simple code to drive an LCD.. Worked great..
Also tied it to a modifed fonera router's serial port and I could access vehicle data form inside the house.. Great for checking GUI code.. I did find out the internal 8Mhz clock could glitch a few characters over the wireless fonera connection but not the 16Mhz??
Still working on my project when I have time but if the sun is shining, I am outside instead of hibernating inside.. lol Plus one of the vehicles I wanted to communiate with uses CAN communication.. Whole different protocol..
Would love it if someone could look at his code and see about making it arduino compatible.. Code is small enough that I don't need two atmega chips side by side but I need arduino for my basic coding abilities..