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.
|06.03.2009: 9-pin adapter|
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.
|06.03.2009: Power cable|
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.
|06.03.2009: Bench testing|
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.
|06.03.2009: 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.
|06.03.2009: In-car connection|
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 ;]
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