Where do you find the day light running module on a 1999 Chevy Suburban?

There isn't a separate "Daylight Running Lamp (DRL) module" in the traditional sense on a 1999 Chevy Suburban. The DRL function is integrated into the vehicle's Body Control Module (BCM). The BCM controls many electrical functions, and DRLs are just one of them.

Therefore, you won't find a specific DRL module to replace or diagnose. Any issues with the DRLs will likely require diagnostics of the BCM itself or checking the related wiring and lamps. A mechanic with a scan tool capable of reading BCM codes will be necessary to properly troubleshoot DRL problems on this vehicle.