Great writeup! This also applies to other OBD2 vehicles. I got this error on my old '99 Tacoma 4x4. The solution was simple.
I had used a K&N drop in filter in the stock Tacoma intake, and after about 15k miles I got this CEL. I was worried I needed a new O2 sensor (not cheap.) But after doing some searching I found info that suggested that K&N filters have a tendency to dirty up MAF sensors. I bought a cheap can of auto electronics cleaner and cleaned up the MAF sensor. Voila, no more CEL.
So if you're using an aftermarket (especially oil based) air filter, you might try looking at the MAF sensor first.