No, the 1999 Oldsmobile Bravada (and its GMC Jimmy/Chevrolet Blazer twins) did
not have a 4-wheel drive switch in the traditional sense. These vehicles used an automatic, on-demand system. There was a dial or selector switch to choose between 2WD and 4WD, but it didn't engage/disengage a 4WD system like a manual transfer case would. The system automatically engaged 4WD as needed based on wheel slippage.
There's no switch to "force" 4WD; the system manages it internally. If the 4WD isn't engaging when you select it, you likely have a problem within the 4WD system itself, needing a mechanic's attention.
