Just finished the second and hopefully my last "weak battery/alternator" learning experience.
In case some of you don't know, a weak but still car cranking battery can send you all kinds of CEL codes. I got some of the weirdest codes and some really weird problems that on the surface had nothing to do
with my battery or alternator. My understanding is that today's cars are much more sensitive to voltage and fluctuation levels.
From this point on, when one of my cars starts acting weird, my first attempt at diagnosis is gonna be to check my battery and alternator health.