The White/GMC J9C0 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 vehicle 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 J9C0 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 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.
Both the 1157 and 194 conform to ANSI standards applicable in the United States and Canada, indicating standardized physical and electrical tolerances across manufacturers.
The front and rear side marker positions on the J9C0 use mechanically incompatible bulb types, as the 1157 uses a bayonet base while the 194 uses a wedge base, making the two non-interchangeable.
The wattage difference between the 1157 and the 194 is substantial, with the 1157 drawing up to 21W on its primary filament compared to the 194's 3.78W, reflecting their different functional roles in the marker lighting system.