Anyone fooled around with interfacing to the OBD II port on vehicles?

[tekart]

I'm thinking about building a device that would need to access vehicle data from the OBDII data port (required in all vehicles in the US since 1996). Has anyone successfully interfaced with the port? Want to share what you learned? It would seem that you first need to determine what type of interface is present; serial, CAN, PWM...

[Charles Linquis]

I have done a bit. It is CAN bus on newer cars.

If you have a BMW, you are really in good shape.

http://autos.groups.yahoo.com/group/HackTheIBus/

[tekart]

What prompted my interest in this is the Scan Gauge II that I use. It is impressive in that it will work with ANY vehicle - so presumably the code can detect which of several possible interfaces are in use for the vehicle. Pretty darned clever device: http://www.scangauge.com
I'd like to explore some applications for vehicles that the SG goes not cover... So solving only for the CAN bus on a BMW would only solve part of the problem.

However I'm open to ideas...

[tekart]

I just poked around the forum looking for CAN bus info and found the ELM327 chip that would seem to solve the whole interface dilemma. It does OBD to serial and the data sheet explains the whole OBD protocol quite nicely. Neat chip!
http://elmelectronics.com/DSheets/ELM327DS.pdf

[Charles Linquis]

Yes, the chip does all the translation. Where the forums help is how to do unusual things, like - how to make your car windows go up and sunroof automatically close when you lock your car.

[retepsnikrep]

I bought a couple of the ELM chips intending to do something clever with them but i haven't yet LOL. I'm interested in ODBII on honda vehicles from 1999-2005 which is basic stuff. I also have a scangauge and looked at putting the elm inbetween it and the car and capturing the signals to work out how it did what it does. There are some good ODBII sites on interwebulator.

My particular interest is IMA ODBII codes for the early Honda Hybrids in particular the Mk1 Insight. These codes don't show on the scangauge and need the proprietory £3000 honda scan tools to acess them. I need to borrow one, capture the signals with the elm chip then make something clever with a pic and the elm.

http://www.thinkythings.org/obdii/
http://www.pureenergysystems.com/sto...TestStatus.htm
http://www.obd2crazy.com/tech.html#eint