What year is your bike ?
It appears you are referring to the HTEV or "exhaust servo" that is associated with the exhaust (a little valve that opens/close within the exhaust, via a servo/cables, to help with proper flow/power, etc (as it was designed from the factory by Honda).
Some people remove them (and add a tune) and might add a "servo buddy" plug to its circuit that disables the "warning" MIL light to trick the computer that everything is still "OK" within the circuit...
You run a search on the board to read more about them or find more specifics in a factory workshop manual as well.