The White/GMC WHLB uses a 1157 bulb size for front side marker applications and a 194 bulb size for rear side marker positions. The replacement chart covers 1991 through 1995 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The White/GMC WHLB uses the 1157 bulb for the front side marker position across the 1991-1995 model years.
The 1157 is a dual-filament bulb rated at 12V with a 21W high filament and a 5W low filament, mounted on a BAY15d bayonet base.
The BAY15d base features offset pins, which prevents the bulb from being seated in an incorrect rotational position and is a defining characteristic that distinguishes it from single-filament bayonet types.
The rear side marker position on the WHLB uses the 194 bulb across the same 1991-1995 model years.
The 194 is a single-filament miniature wedge bulb in the T10 form factor, rated at 12V and 3.78W.
The T10 wedge base relies on the tension of the socket contacts rather than a locking mechanism, which is a standard trait of low-wattage miniature wedge bulbs in this class.
Both the 1157 and 194 conform to ANSI standards applicable in the United States and Canada.
The 1157 and 194 are not interchangeable with each other, as they differ in base type, filament count, wattage, and physical form factor.