I've played through all of Arkham Asylum and I still don't remember how to do this - I see question marks all over the place in detective mode, but holding down "L2" doesn't seem to scan them no matter how I try to align it. (I don't even get a "misaligned" message.) How do you scan the question marks?
You need to be able to interrogate Riddler informants. The scan feature unlocks after you question the first one, I think.
I had the same problem when i started the game! Once you enter one of the first areas in the story mode, the "scan" option opens up to you. You're prompted to scan two trophies locked in an elevator shaft so you can come back to them. Once you do that, you'll be able to scan whenever you'd like. Confusing, but that's how it goes.
Got it ! Just hold the same button down that you used to invoke detective mode, while aiming closely at a riddler trophy.
How could i forget. Landed here too, before figuring it out. Playing on Onlive, in that case that means -> Hold the LB button to scan when you already are in Detective mode ;)
Which is also described in the cotrols pause menu
Also dont forget your DLC skin switching code ;)
To use the code, the following button combination must be pressed on the Main Menu screen after a save slot has been selected:
Left, Left, Down, Down, Left, Left, Right, Up, Up, Down
You'll hear thunder if done correctly
You should still be able to line up a green question mark while in detective mode and scanning it. You need to hold down the detective mode button to scan it. LB on 360, and L2 on the PS3.
If you're not getting any type of message about nothing being found, or misaligned, then likely something else is going on.