Third brake light has no voltage

[RyanS]

I have a 2018 Tahoe Premier. Third brake light had a crack in it, got water in it and stopped working. I replaced the light, doesn’t work. I check for voltage at the connector while the brake pedal was engaged. Nothing. I checked the connection on the inside of the vehicle in the ceiling. Nothing. There is no fuse labeled for third brake light. Just left and right. I proceeded to test every fuse with a volt meter. Under the hood, drivers side, passenger side and rear locations. Didn’t find any bad ones. Anyone have any insight?

 

[Doubeleive]

I have a 2018 Tahoe Premier. Third brake light had a crack in it, got water in it and stopped working. I replaced the light, doesn’t work. I check for voltage at the connector while the brake pedal was engaged. Nothing. I checked the connection on the inside of the vehicle in the ceiling. Nothing. There is no fuse labeled for third brake light. Just left and right. I proceeded to test every fuse with a volt meter. Under the hood, drivers side, passenger side and rear locations. Didn’t find any bad ones. Anyone have any insight?

look on the gm upfitter guide, they have a more detailed explanation of which fuse does what, some fuses power things that are not labeled as such in the owners manual
probably still a fuse.
also if you tested for voltage at the brake light connector after the vehicle has gone into sleep mode it won't have any power. try again with the key on.
on previous models it didn't matter when you pressed the brake pedal on this generation it does, after 2-3 minutes with the key off the brake lights will not come on by pressing the pedal anymore. I found this out testing things myself.

 

[Fless]

As little as I know about reading these, it looks to be powered by the BCM. Check BCM1 fuse?

Upfitter guide here: https://www.gmupfitter.com/wp-content/uploads/2021/07/18_Escalade_Body_Builder_SM_U_2017JUL24.pdf
(Diagrams for the CHMSL start on page 38 of the PDF)

 

[RyanS]

look on the gm upfitter guide, they have a more detailed explanation of which fuse does what, some fuses power things that are not labeled as such in the owners manual
probably still a fuse.
also if you tested for voltage at the brake light connector after the vehicle has gone into sleep mode it won't have any power. try again with the key on.
on previous models it didn't matter when you pressed the brake pedal on this generation it does, after 2-3 minutes with the key off the brake lights will not come on by pressing the pedal anymore. I found this out testing things myself.

I had the vehicle on and other brake lights engaged no issue. Where can I find a GM up fitter guide? Never heard of it.

 

[RyanS]

As little as I know about reading these, it looks to be powered by the BCM. Check BCM1 fuse?

Upfitter guide here: https://www.gmupfitter.com/wp-content/uploads/2021/07/18_Escalade_Body_Builder_SM_U_2017JUL24.pdf
(Diagrams for the CHMSL start on page 38 of the PDF)

View attachment 427261

Thanks

 

[RyanS]

As little as I know about reading these, it looks to be powered by the BCM. Check BCM1 fuse?

Upfitter guide here: https://www.gmupfitter.com/wp-content/uploads/2021/07/18_Escalade_Body_Builder_SM_U_2017JUL24.pdf
(Diagrams for the CHMSL start on page 38 of the PDF)

View attachment 427261

Checked BCM 1, tested good, looked good, swapped out with new one, still no third brake light.

 

[RyanS]

Checked BCM 1, tested good, looked good, swapped out with new one, still no third brake light.

Checked all three BCM fusee and they’re good.

 

[Doubeleive]

you might want to get a meter out and start probing then, the fuse should have done it's job but if it didn't then there is a melted spot somewhere or a break in the wire.
trace the ground first.

 

[RyanS]

you might want to get a meter out and start probing then, the fuse should have done it's job but if it didn't then there is a melted spot somewhere or a break in the wire.
trace the ground first.

Not that. Could BCM need to be reprogrammed?

 

[Doubeleive]

Not that. Could BCM need to be reprogrammed?

no, you traced the ground and power with a meter? checked for continuity?