Just incase someone needs this info

Lighting - Mirror Turn Signal is Inoperative

Bulletin No.: 07-08-42-013
Date: September 07, 2007
TECHNICAL
Subject:
Turn Signal in Camper Style Outside Rearview Mirror (RPO DPN) Does Not Illuminate Turn Signal Flash (Replace Upper Mirror Glass) Models:
2003-2006 Chevrolet Avalanche, Suburban, Tahoe
2003-2007 Chevrolet Silverado Classic
2003-2007 GMC Sierra Classic
2003-2007 GMC Yukon, Yukon Denali, Yukon XL, Yukon Denali XL Condition
Some customers may comment that the turn signal in the camper style rearview mirror (RPO DPN) does not illuminate the flash.
Cause
The signal unit adhesive may not be fully seated to the back side of the glass.