So I was told during a check-up at a Jiffy Lube oil change that their analysis turned up a failed alternator giving 12.1V. Given that Jiffy Lube doesn't replace parts and thus gains nothing if I do, I would be inclined to agree.
However, I want a second opinion on this. Is 12.1V for a Toyota Avalon '97 considered failing by spec? What is the spec range?