These modules have been in production since just before the turn of the century, but if you still don’t understand their functions diagnosis will be more difficult than it has to be.
A look at the MR16DDT turbocharged, direct-injection gasoline engine in the JUKE, covering the engine design, direct injection system, turbo, and continuously variable valve timing. Also, a few service procedures and diagnostic considerations for this engine.
There are some things that are just part of the program, like not recalling things as well as you once did as you put on a few years (okay, more than a few…). It seems I just can’t remember it all now.