What is the "box' on the N2 head unit wiring harness that the yellow and black wires run through? Is this some kind of filter, and is it necessary?

Thanks,

correct me if i'm wrong (i only have a D2) but i believe its a fuse box..my d2 had the same thing

No, it is not a fuse. The harness (2nd bought over eBay after I got shafted on the first one) has a fuse downstream from this plastic 2-inch long, 1-inch square box. It will not open. Both the yellow and the black ground wires run through it.

Any ideas anyone?

No, it is not a fuse. The harness (2nd bought over eBay after I got shafted on the first one) has a fuse downstream from this plastic 2-inch long, 1-inch square box. It will not open. Both the yellow and the black ground wires run through it.

Any ideas anyone?

I've never taken mine apart, but I'd say it's very likely an RF choke used for noise filtering. It could have diodes in it too to protect against reverse polarity. I wouldn't recommend removing it.

Yeah, it's a noise filter. I opened one once awhile back for a different HU and there was a largish choke inside. Looks like a small transformer.

It should work fine without it, but it's good to have so I wouldn't remove it.

it is a noise filter can be removed but mat cause engine noise in some amplified factory systems

Thanks, guys. I'm learning...slowly! Hope to get it installed this weekend.