Here's a brief guide on how to connect to the CAN bus on a Trionic7 ECU.
CAN bus connection offers a fast and convenient way to read or flash the
firmware in the ECU. However, keep in mind that there's a slight chance it
may fail while writing the memory, especially if you're flashing in the car.
When that happens, you end up with a dead ECU, which no longer responds to
a CAN connection. The only way to revive it in this case is by using a
Lawicel CANUSB seems to remain as
the best (if not the only) CAN-USB adapter supported by the community
right now. You can also try RS-232 devices, but you may be
hard pressed to find a laptop with a serial port these days.
Next, you need a female 9-pin D-sub connector. You're only interested in
two pins here: #2 (CAN low) and #7 (CAN high). I'm using white and
green wires to match the colors of CAN low and CAN high leads on the
instrumentation bus in the Saab.
If you plan to connect to the ECU on the bench, you will also need to power
it up. There are three pins each where you need to apply ground
(#25, #47, #62) and +12V power (#1, #23, #43). I made this simple
harness with insulated alligator clips.
Hook up both the power harness and the CAN harness (pin #19 is CAN low,
#66 is CAN high). Attach a power supply. It may not hurt to
have slighly more voltage - these 16V IBM ThinkPad AC adapters seem to work
great. Once it's powered up, start your software and proceed with
connecting to the ECU.
ACC unit harness
There is a number of locations in the car where you can access the
instrumentation bus: the SID, the stereo, the ACC, the CD changer, etc.
I chose to unplug the ACC panel since I can live without it while tuning.
Connect your green "CAN high" wire to pin #33 on the ACC harness, and
your white "CAN low" wire to pin #34. Turn the ignition key, and enjoy
a live connection to your ECU.
P.S. Perhaps it's time to clean the screen on my laptop ;]