Originally Posted by
pendell
When you're debugging software, the answer is "no". It can sometimes take many experiments and tests to isolate the problem, which can then be corrected.
I've seen the same thing in the auto shop; While a mechanic may have a reasonably good idea what the issue is, a lot of times it's still a good idea to check the onboard diagnostics before opening 'er up. And in a few cases the symptoms could result from a number of different problems, and it will require some experiments to narrow it down before a proper diagnosis can be made.