Help on sub output control

[Sonus]

Anybody can tell me if is there a way to adjust the sub output level ?
Or by a service menu on the radio unit or by a trim pot somewhere in the system ?

I've look at the amp under the passenger's seat and on the sub speaker itself where there is another kind of amp or xover unit but did not find any adjustments !?

 

[Newf]

I am convinced there is a service menu somewhere. But I haven't heard of anyone finding one.