Hi,
Here is a link to the service manual for your laptop. Unfortunately it makes no mention of an individual blue wire. However if you scroll to p.38 it details what the beeps mean and this may help you resolve your problem.
Also try tracing the blue wire to the other end. Where it is coming from (or going to ) may give you an indication of what it is for.
https://content.etilize.com/User-Manual/1022569150.pdf
Hopefully this is of some help.