OBD II info

[Mike Fahrion]

> http://www.sae.org/PRODSERV/stds/J2201.htm - OBD-II interface description
> http://www.sae.org/PRODSERV/stds/J1850.htm - Communications protocol
>
>Each of those docs is $62. Now, I'm not overly motivated to shell out $60


If you do get motivated to do it, spend $75 instead to purchase SAE's
HS-3000 1998.  This is a bargain (relatively), it has *every* spec related
to OBDII you'll ever need, except for the ISO 9141 stuff but Ford doesn't
use that anyway.

>Well, I did a little more surfing and found:
>
> http://chimera.acs.ttu.edu/~z7d23/research.html
>
>which seems to be a copy of J2201. This mentions that there are 3 possible
>communication protocols that a DLC can connect on (two of which are J1850
>variants, the third is an ISO communications standard). I also found:

Three hardware layers are allowed for use in OBDII, from a hardware point of
view, they have pretty much nothing in common with each other.

SAE J1850 VPW - used by domestic GM's
SAE J1850 PWM - used by domestic Fords
ISO-9141 used by Chrysler and most imports

As with every sure thing, there are some exceptions - there's further info
on this at www.obdii.com

-mike