You should have gone to Autozone or any of the other discount auto parts places when you saw the first Check Engine Light...they'd pull the codes for free. Copy em down, and research em on net--easy.
Like Muss said, a loose gas cap will throw a CEL--and that code WILL clear itself from memory, after so many cycles where the evap emissions system pulls a good vacuum, with 'good' readings. It's entirely possible that was the first CEL you saw, and why the shop saw no codes.
At this point, you can't tell what the heck gave you a CEL initially. Codes like O2 sensors will not clear, and the CEL won't go off, so that's one you can scratch off the list. You didn't specify the other codes pulled, so no opinion on them.
The year-later codes are likely totally unrelated, and independent from your initial CEL. If the vendor decides to take on the repairs at their expense, lucky you.
BTW, OBD is an industry-wide protocol. The codes vary slightly from mfr to mfr, but any OBD reader will read any OBD-compliant car (anything legal for sale in US).
Like Muss said, a loose gas cap will throw a CEL--and that code WILL clear itself from memory, after so many cycles where the evap emissions system pulls a good vacuum, with 'good' readings. It's entirely possible that was the first CEL you saw, and why the shop saw no codes.
At this point, you can't tell what the heck gave you a CEL initially. Codes like O2 sensors will not clear, and the CEL won't go off, so that's one you can scratch off the list. You didn't specify the other codes pulled, so no opinion on them.
The year-later codes are likely totally unrelated, and independent from your initial CEL. If the vendor decides to take on the repairs at their expense, lucky you.
BTW, OBD is an industry-wide protocol. The codes vary slightly from mfr to mfr, but any OBD reader will read any OBD-compliant car (anything legal for sale in US).