2010 Prius interior lights; homelink and VSC traction control not working

Hello techies!
I have a tough electrical issue here for my 2010 Prius.
At the same time my interior lights, Homelink and traction control stopped working. The traction control light is still on. I tried fuses but to no avail. I finally took it into the local Toyota dealer to do a diagnosis. They still have not fixed it. They are telling me to replace the Dash Harness, which is a $3,000 part + labor. The mechanic found there was a voltage drop before the interior light components as it was only getting 0.9 volts. He traced the circuits and found the voltage drop occurring inside of the the Dash Harness after the fuse block assembly. Also there was only 0.9 volts to the steering angle sensor causing the VSC Traction Control light to come on. He also checked the rearview mirror and it is functioning properly.

The weird thing is everything stopped working maybe 60 days ago. Then 2 weeks ago, everything started working, then after a few days stopped again. It seems to me that there is a short in a wire or a couple wires are touching?
Any ideas on how to fix without spending $3-$4k on a 10yr car to have the lights on and traction control?

 

So I just checked my Prius diagnosis and it is reading 11.4V on the screen. Then I took a multimeter to the 12V battery and it is only reading 12.1V. I think you may be right. Let me go to AutoZone for a double check and see if still low. If it is I will replace and report back.

 

I think you are correct Pluggo. I took my Prius to the dealer for a batter check and all fine; as it is reading 12.7v. Not sure what to do next as the dealer is still stating that there is a drop in voltage prior to the dash harness. And they said the dash harness was a $3,000 part. yikes! Any other ideas? I live in Northeast Ohio.

 

Thank you Pluggo. Is there a link on the site or do you have a link to a video on how to remove the Dash to get to the Dash Harness for my Gen3 Prius? I would rather do this tedious work versus paying the Toyota dealer to burn hours. Appreciate your assistance.