Third brake light on 03 Tahoe

To echo what Gary said, third brake light on my 04 Tahoe stopped working. It is a sealed module with LED's. No user replaceable bulbs.

http://www.amazon.com/gp/aw/d/B000TYQB14

Dealer wanted $250. The amazon replacement I installed is side by side identical to OEM for $40 and still working 2 years later.

If you determine the light itself is the problem, check out Amazon for a replacement. They are about 10% of what the dealer charges. Yeah, it's a off-shore cheapy but, the one I put in a couple of years ago is still doing its job.
Gary

If your model has it. Clean the connectors too on that bank of prongs that connect when you close the back door.

In the fuse box near the driver side door there is a fuse labled: VEH CHMSL (Vehicle Center high mounted stop lamp).

Found that info on a Google search.

Diagram that I looked at shows it about in the center of the under dash fuse block. Diagram says it is marked "VEH CHMSL" should be 10 amp.
It appears to be right above the 12 pin Body control module that it says is brown.
Not sure if this link will work.
Fuse block

Also check to see if the bulbs are burned out.

Do you know where it is located? Thanks

Yes, it is a separate fuse. It should be marked "CHMSL" Center High Mount Stop Light