I just checked on my sons mitsu evo…..no cap. Not on top, not on bottom.
FWIW the controller on my Skyline that had the cap (but to D3) is a silver and black unit. The controller on my sons is one of the translucent controllers.
I have one of those super bright LED lights….you cansee through the translucent controller with it to look for the cap. I took it apart just to check it out anyway….