The White/GMC J8C0 features a 1157 bulb size for the front side marker and a 194 bulb size for the rear side marker. The replacement chart covers 1988 to 1989 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 J8C0 uses two distinct bulb types across its side marker positions for the 1988-1989 model years: the 1157 at the front and the 194 at the rear.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W output, meaning it operates one filament for steady illumination and a second, lower-wattage filament for a reduced-intensity function.
The BAY15d bayonet base on the 1157 features offset pins, a design that prevents incorrect insertion by ensuring the bulb can only be seated in one orientation.
The 194 is a T10 miniature wedge bulb rated at 12V and 3.78W, a single-filament type commonly used in low-intensity marker and clearance lighting applications.
The wedge base of the 194 requires no locking mechanism, as the socket itself holds the bulb through friction, distinguishing it physically from the bayonet-style 1157.
Both the 1157 and 194 conform to ANSI standards applicable in the United States and Canada, indicating standardized electrical and physical tolerances across manufacturers.
The 1157 and 194 are not interchangeable with each other, as they differ in base type, wattage, filament count, and physical form factor.
The front and rear side marker positions on the J8C0 draw notably different wattages, with the front 1157 consuming up to 21W on its primary filament compared to the rear 194 at 3.78W.