I love flow charts like this, just at step 3 they hint replace ecm. Stupid and useless chart, but that is all that is available. The rest is experience I guess, oh, and tooling.
If you don't have access to a scanner, try something with elm on board. If you lived close to me, I have a high end scanner I want to give away, does subaru all day long. Update is 2012, you would love this briefcase.
Disregard comment on GRC, I might have confused that with another thread, or the chart somehow diasapeard. Anyway, you now have one.