Mechanical elaborated

As per the last post... there are two possible explanations for the difference. One is of course that the dealership is essentially ripping me off, recommending work that doesn't really need to be done, and charging lots for it. The other explanation is that the independent mechanic just did not see the problems, perhaps not knowledgeable enough. I think it's mostly the first case, but maybe a little of the latter case.

For the general mechanical work, things the dealership just happened to notice when snooping around but that independent guy figured looked ok, I figure things are probably fine. The problem is the original reason I took the car in: the check engine light came on. The dealership had said the ECM needed replacing. At least the independent guy showed me the code so I could see it reporting "P0507: Engine idling faster than expected." He said it looked to be idling around the right range, and didn't have much else to say about it, just keep an eye on engine idle speed, if it seems fine, don't worry. The issue with that is that the light turned on, the dealership reset it when I took the car in, but it turned on again about a week later, so the independent guy reset it also. But I don't like the idea that it will keep coming on in the future, even if he thinks it's nothing to worry about. I don't consider the problem solved.

But at least with that engine code I was able to research online. I downloaded the service manual for my car, so I could see how the dealership arrived at the conclusion to replace ECM. Of course, don't know if they really followed that procedure closely. Other people have solved a similar issue by performing an "Idle air volume learning." Hmm, the dealership would have needed to do this when they flashed the ECM as part of a recall a few months ago. Maybe they didn't do it right? Maybe it's temperature dependent? Anyway, the light came on again recently, so, finally I decided to perform that procedure and see what happens. Of course now the light is on, I'll have to get it cleared then can wait to see if it comes back in a couple weeks or if that procedure solved it.

That procedure is interesting in itself though... With the car 'warmed up' and all battery-drawing accessories off, turn the key to off for 10 seconds, then turn to on and wait 3 seconds, then hit the gas pedal fully 5 times within 5 seconds, then wait 7 seconds, then fully depress the gas pedal for about 20 seconds, until the engine light flashes for a while then goes solid, release the pedal within 3 seconds of it going solid, then start the engine and wait. Was weird to see it revving up and down by itself without touching anything, eventually settled at a nice normal idle speed. Revved the engine high a couple more times, and that's about it.