Possibly a bad ground wire?

[Tred26]

I have a 99 2dr 4x4 tahoe. Everytime i use my turn signals my needle on the battery gauge moves along with the turn signal. Also my passenger side taillight is always dimmer than the drivers side. I have replaced a section of the wiring harness on the tail light but still the same outcome. I have also gone through and grinded down all the ground wires under the hood.
Trying to figure out what else i could do. Has anyone come across this issue in the past?

 

[SunlitComet]

how about the ground wires in the back? or a corroded bulb socket perhaps?

 

[moviewithnotitle]

Where are those grounds for the taillights located? I have a similar issue, and also show a volt meter change when I apply the brakes. Grounds up front have all been replaced...but the back is still a little mystery to me.

 

[SunlitComet]

look below for all the locations.

 

[SunlitComet]

g401 is the taillight one.