Black Wire Above Emergency Brake Pedal

[Luker1]

Anyone know what this black wire with red connector is for? About a month ago it fell down from above the e-brake pedal on my 2017 Sierra (I moved it out of the way under the floor mat). Can't see anything obvious that it came unattached from. Possibly something to use for connecting a diagnostic tool?

 

[mogleybear]

Kind of difficult to tell from the picture, but my guess is it was something installed aftermarket. That looks like an in-line fuse holder but I can't really tell.