I would like to make a tool for scanning the OBD II (On Board Diagnostics 2)
system in my cars engine management unit.  I believe the system is CAN based
and that the protocols are standard but don't seem to be able to find much
about it  on the web. Could someone please point me to information about how
to do this, ideally with a PC or with a PIC microcontroller? Is there a
published Spec available?

Thanks,
Gerry Cox