The White/GMC WIA front side marker uses a 1157 bulb size while the rear side marker requires a 194 bulb size. The replacement chart covers 1988 to 1995 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 WIA uses the 1157 bulb for the front side marker position across the full 1988-1995 model range.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W output, and conforms to ANSI standards recognized in both the United States and Canada.
The BAY15d bayonet base features offset pins, a design that prevents single-filament bulbs with similar bases from being seated in its place, making filament count a critical factor in fitment.
The rear side marker position on the White/GMC WIA calls for the 194 bulb across the same 1988-1995 span.
The 194 is a miniature wedge bulb in the T10 form factor, rated at 12V and 3.78W, and also carries ANSI certification for the US and Canadian markets.
The T10 wedge base relies on the bulb's own leads for retention rather than a locking mechanism, which distinguishes it physically from the bayonet-style 1157 used at the front.
The 1157 and 194 are not interchangeable with each other, as they differ in base type, wattage, filament count, and physical form factor.
The significant wattage difference between the 1157 (21W/5W) and the 194 (3.78W) reflects their respective roles, with the higher-output dual-filament unit at the front and the low-draw wedge unit at the rear.