Do you guys know of a good site or sites with information on making homebrew readers for the OBDII ports and the info available there?

I can handle both the hardware and software, but was hoping for some kind of a better starting point than google was able to turn up.

Im not so much interested in messing with the car as just playing with the info, etc.. as a side/hobby project.

Thanks!

7/1/2009 6:52:35 PM

http://en.wikipedia.org/wiki/On-Board_Diagnostics#Signal_protocols

you're looking for stuff like this?

here's a decent paper on ECU communications at NI

http://zone.ni.com/devzone/cda/tut/p/id/3064

7/1/2009 8:02:49 PM

most frustrating thing about OBD II stuff is that many/most cars can only log at the 5 hz minimum sample rate depending on how you connect to them. Which is slow as piss. And you have to remember that OBD II isn't just "obd II" , it's a collection of different physical protocols, two of which come in a high and low speed form.



If you are interested, i have SAE J1978 ("OBD II Scantool") and J1979 ("Diagnostic Test Modes"/PID list), and J1850 "Class B Data Communications Network Interface." I've skimmed through them, a lot of them are very technical.

7/1/2009 8:29:41 PM

I've got a chinese ELM327 clone running PCMSCAN software on linux(it took a good bit of hacking and trial and error to get this working under WINE). Works great on everything I've tried so far(VPW, PWM, ISO). Haven't tried it on any 2008/09's at the moment. $23 straight from hong kong, by the way.

Before this I was using scantool.net's free open source software, which is crippled and basically crap(the new version won't even connect to unlicensed clones). With that software I had trouble connecting to any GM newer than 2003 and a few others.

OBD-II is such a screwed up cluster of a "protocol". I was really disappointed with the total lack of open source OBD software out there.

[Edited on July 1, 2009 at 8:46 PM. Reason : .]

7/1/2009 8:42:21 PM

^ As of the 2008 model year I believe all new cars communicate on the CAN protocol and the mismatch of hardware and software will slowly fade.

7/1/2009 9:02:04 PM

Nah, they'll just keep increasing the canbus speeds and we'll all still have to buy new scan tools every few years.

7/1/2009 11:09:11 PM

Wow, I had no idea it was that disorganized.

I assumed (wrongly) that OBD II standardized everything.

Thanks for pointing me in the right direction, this at least gives me a starting point to play with.


As a side note, I did find this IC:

http://www.elmelectronics.com/DSheets/ELM327DS.pdf

Looks like it handles most all of the different systems/protocols for you, which, on the surface, seems to be the piece I need to put at the center of all this. I've only read a little about the chip, so I may be mistaken.

[Edited on July 1, 2009 at 11:17 PM. Reason : .]

7/1/2009 11:15:17 PM

hang on, argx is looking up a 10 page answer

7/5/2009 6:09:51 PM