I was always told it was a low fuel pressure thing. That you really just scare the computer, it throws a light at you to make you stop. You stop, and the light goes away after a few minutes of driving normally. Thats the way it works in my truck. I don't know if it hurts anything or not to be honest. I think it's pretty common with chipped/programmed trucks where the fuel limitations are removed.
AIH is Air Intake Heater.
The PCM will activate the AIH to reduce white smoke during long idle periods at low ambient temps.
Some people plug theirs, since you threw a PO541, that's the only reason I asked if you did.
Good Luck
chris