I've just got one Kenwood external amp.
Same one I've always had, and its not even all that powerful.

Your comment about the battery may be something though.

I've been wondering when my battery was gonna go.

Its the same battery the car came with back in November of 1994.
By all rights it should be dead as a doornail by now.
7+ years on a stock VW battery!?

Would a dying battery trigger the icon though, even if the car is running?

Z~