2015 gmc sierra brakes and turn signals arent working

[Santiago1911]

Hi I've been having problems with my 2015 gmc all terrain, the running lights are on but the brake lights and rear turn signal lights wont blink. All 4 lights turn on . The third brake light on top of the bed does work. I’ve bought new harnesses and have checked the grounds on the truck and have cleaned them out also. The fuses seem to be good , what could be the problem, i need help its a hazard driving like this without brake lights 

[newdude]

18 minutes ago, Santiago1911 said:

Hi I've been having problems with my 2015 gmc all terrain, the running lights are on but the brake lights and rear turn signal lights wont blink. All 4 lights turn on . The third brake light on top of the bed does work. I’ve bought new harnesses and have checked the grounds on the truck and have cleaned them out also. The fuses seem to be good , what could be the problem, i need help its a hazard driving like this without brake lights 

 

 

You got new tail light harnesses?  Did you replace the bulbs?  

[Santiago1911]

1 minute ago, newdude said:

 

 

You got new tail light harnesses?  Did you replace the bulbs?  

I did not replace the bulbs they did look burntbut still light up, could that be the issue? 

[newdude]

4 hours ago, Santiago1911 said:

I did not replace the bulbs they did look burntbut still light up, could that be the issue? 

 

 

They are dual filament.  One is standard for running lights, the other filament handles the brake/flasher.  One filament can burn out causing tails but no flash.  

Edited October 22 by newdude

[Santiago1911]

6 hours ago, newdude said:

 

 

You got new tail light harnesses?  Did you replace the bulbs?  

I will check it out tomorrow, thank you