tach display

question regarding 2004 round digital tach, on f150. when i turn on ign switch it goes thru self test and every thing is displayed, then 1 second after every possible item that was indicated clears the engine icon comes on in top right corner next to trim bars. this indication has no reference in my operaters manual, but when looking at 2006 manual it is a check engine light.
this icon stays on when running also, any ideas?

[boats.net]

It's the water in fuel warning, check the fuel filter for water. If your motor does not have water detection sensor in fuel filter on engine then you would have to take it to your dealer to the light to go off.

thanks for info, much appreciated and there is not a sensor on filter.