Exhaust control valve ..
If it's been stood for while it might be seized ..
It's attached to two cables that are connected to a servo motor, if the motor doesn't achieve its full movement cycle it'll throw up a fault.
For your info, if you don't get it fixed the plastic sprockets/cogs in the servo motor will eventually jump and strip rendering the servo useless.
If you want to use the bike disconnect the cables at the servo end, this will trick the ECU into thinking the servo is doing its job as it will comple it's movement cycle , your fault will then disappear.
Oh .. the exhaust valve, when free, sits in the open position so , if you free it the spring will hold it open