2001 Accord V6 about 117,000 miles.

While driving into work this morning I saw that my D4 indicator light was dimming intermitently. It was going from bright green to a lighter green maybe about every 15-20 seconds. It was not consistent, and was not "blinking". Any ideas what this might be??

 

Probably something drawing a large electrical current, although I have no clue what it is.

It's not a transmission problem, which is good.