OBD_II You asked for experiences

[Dave Hempstead]

Wayne MacDonald described what he found with the seeds and the security
for the OBD-II codes.


This is fascinating, because what I've seen in the OBD-I  codes are
similar yet different.

For OBD-I, it uses the same external scheme for security.  You get a
seed back from the PCM, then
you send it a code based upon that seed.  However, the difference is
that the code you send back is
simpy a one's complement of the seed.  Now, I've only seen this on one
PCM, but I've also looked at the
code inside the OBD-I PCM, and it appears to match.


So, it looks like they've implemented a much tougher security method,
but kept the same ALDL
interface.


Wayne, would you care to send me the tables you've uncovered so far.
I'm curious what the
seed-to-security-code mapping looks like.


Also, we've got a guy on the list here reverse engineering the 96 OBD-II
PCM code.  He should be
able to describe the algorithm.


Dave Hempstead