What? My third brake light won't work at all after installing my Impala CMD third brake light. Any ideas? This sucks. WHAT I'VE ALREADY TRIED in no particular order:

1:Inspected all fuses on BCM/interior fuse panel. None are blown.
2:Tried all three other CMD strips I have with the same results.
2.5:Plugged the CMD strips into my driver taillight and they all work fine!
3:Removed and reinstalled all three BCM relays
4: Multimeter! I tested voltage on the plug of the third brake light. grounding to the plug itself yielded 6.75V. Then I grounded it on my tail light ground. The black wire was putting out ~14 volts(wtf? isn't it supposed to be 0v?) and the blue wire was putting out only 7.

I'm really lost here. I'd love to have a third brake light again, especially after putting the work into my CMD conversion.

 

Reverse the connection? Is a stupid idea, but won't hurt trying lol

 

Yeah I've done that too lol. Didn't work.

 

If this happens to anyone else, pull the fuse cover under your hood and look for "CHMSL" and check that fuse. It's what fixed my problem even though no fuses in the BCM are blown.

 

That's what happened to me and it worked just fine and has for over 3 years now. Good luck op.

robk