My reverse lights and 3rd brake light dont work, i even put all new lights in and they still dont work. Does anyone know why they are doing this?

 

Does your dash lights work? They are all in the same circuit, along with the license plate light. Fuse could be blown. I believe its the park lamp one either a 10 or 15 amp.

 

Dash lights work, license plate light works, And my park lamp fuse isnt blown

 

Then trace your wires and check your grounds and connections. You can find detailed schematics online that can help.

 

Maybe the reverse switch? idk

https://www.cobaltss.net/forums/how-...ch-mu3-222552/

 

Check for power and ground at connectors. Thatl tell you which circuit to trace.
what car do you have and ill get a connector end views for you too

 

A little more information as to what your car is would help a lot in troubleshooting.

I doubt the two problems you have are related.

 

I have a 2007 cobalt ss 2.0

 

Reverse lights

1 is light green and should have 12v when your in reverse with key in run position
2 is black and should be ground at all times.

3rd brake light

A is light blue and should have 12v with brake pedal depressed.
B is is black and should be ground at all times

problems are not related except for at g401 and 402. they are either spliced there or multiple ground eyelets on one bolt, could be a potential place for problems but not likely. check for power first.