Coolant light when engine off

[MrGraphics]

I have a 2009 128i with 62,000 miles. I'm very mechanically inclined, but this one has me stumped. When I start up the car and drive, no problems. However after a long-ish drive, when I shut the engine off, that's when the yellow coolant light comes on.

Coolant levels are good. The light never comes on when driving or if the engine is running. Again, it only comes on right after the engine is shut off.

Ideas? Water pump starting to go? I did a search but nobody seems to have this skew of issue.

[MarkkyyMan]

When did you last change the coolant?

[jcoop269]

Honestly, I'd think that was a coolant service light of some kind but I wasn't sure there was one considering it is a "lifetime" fluid(though many feel lifetime=100,000 miles).