plug in between 2 ECU connectors?

Hi guys,

I got a 2001 F4i. I took my battery out trying to winterize it and i found an unplugged wiring connector between 2 big ECU wiriing plugs. Do you guys know what is that plug? Should I plug it into somewhere?

thanks
William

it's a tiny little plug right? like a bit more than 1/4" wide? there's this loose connector just there...and nothing plugs into it...i'm not sure what it's for, but it's where you decribed.

I believe it's a plug in for the diagnostic reader.

^
Yeah, it is a test connector.