On Board Diags
OBD-II is the protocol used by all cars built after 1996. If you want your PC or laptop to read some of the data from the "Computer" in your car then you need some kind of OBD to RS-232 interface. There are many OBD-II interfaces out there, but most of them are very expensive. You can make your own interface if you know a bit about electronics and know how to make your own PCB boards.
The interface board uses the Elm Electronics ELM OBD interface chip. I didn't add anything special to the schematic, so it's pretty much identical to the one in the data sheet. If anyone is interested to have the schematic I can email them to you. So far I've made a board using the ELM 322 & ELM 320 chips. These two single sided PCB boards where made using Eagle PCB software and Press & Peel. The ELM 322 OBD chip is for GM CARS ONLY and the ELM 320 is for FORD CARS ONLY. I'm working on the ISO version for all other cars.
So far I've tried the boards and OBD-II logger on a 1999
Grand Prix, 1998 Grand Am and 2002 Ford Explorer without any obvious problems.
Comments from emails shows that it works with:
Please let me know your results... firstname.lastname@example.org
OBD-II Logger also works with Scan tools boards. But remember, they'll support their software on their hardware.
There is a Perl version and a Windows version