If your panel is the same as mine in an L 3560, and you are talking about the engine symbol with an exclamation point in it, my manual says it is either engine overheat, which it sounds like you've ruled out, or problem with your ECS computer. It says (helpfully) contact your Kubota dealer

.
It said that the engine output may be normal, but if it is not to put the tractor away and and stop the engine.