OBD-II

[Steve=Ravet%Prj=Eng%PCPD=Hou at bangate.compaq.com]

Craig Pugsley <c.pugsley at trl.oz.au> Wrote:
| Steve Ravet wrote:
| > It's more than that, it also defines a standard one or two wire 
| serial bus 
| > that the ECM uses to communicate with sensors and other 
| equipment (including 
| > diagnostic equipment), and a standard for the information 
| packets that are 
| > placed on the bus.  So one diagnostic computer will work for 
| all cars.  This 
| > would indeed be a good feature to include on a diy-efi computer.
| 
| Is the 2 wire serial bus structure the same as the CAN bus developed by
| Bosch as a comms system for motor vehicles? Motorola have (according to
| the article) a 68HC705X4 with a CAN interface. Also according to the
| article it is different to the J1850 bus.
| 
| Craig.
| 

No.  the single wire bus is based on GM's DLCS variable pulse width 
modulation, 10.4kbps.  The two wire bus is based on Ford's HBCC bus, pulse 
width modulated, 41.6kbps.  These are both laid out in SAE J1850.  Outside the 
US, Bosch has developed CAN, which corresponds to ISO 9141.  Peugot has 
developed another methond, called VAN, which does not appear to have been 
adopted by any standards committees.  I don't have any details on the CAN bus, 
but it appears that it will only be used outside the US.  This info is from 
the August 15 EDN Products Edition.

-steve