I think there are few things wrong with your equation.
Where do you post this? In one of the answer options of the second questions, I assume?
Multiple choice questions work a little different than other questions. You need to check if Q1_SQ001 was marked Y I think.
I think this should work (not tested):
Code:
{if(Q1_SQ001 == "Y", "SQ001.shown",""}
"shown" is necessary to show the answer option, otherwise I think it will only show "Y", which is the answer to that subquestion. And you need the empty "" at the end, because you need something for the "else".