The White/GMC WIM features front side marker bulbs in 1157 size and rear side marker bulbs in 194 size. The replacement chart covers 1988 to 1994 production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The White/GMC WIM uses two distinct bulb types across its side marker positions: the 1157 for front side markers and the 194 for rear side markers, covering the 1988-1994 model years for both positions.
The 1157 is a dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
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 dual-filament configuration of the 1157 allows a single bulb to serve two lighting functions at different brightness levels, which is why it is a common choice for front marker positions that may also carry turn signal or parking light duties.
The 194 is a miniature wedge-type bulb in the T10 form factor, rated at 12V and 3.78W, and it uses no base pins, relying instead on the wedge shape of its glass envelope to make contact within the socket.
The 1157 and 194 are both ANSI-standardized bulbs recognized in the United States and Canada, meaning their electrical and physical specifications conform to a defined industry standard rather than a proprietary format.
Because the 1157 and 194 differ in base type, wattage, and filament count, the two bulbs are not interchangeable between the front and rear side marker positions on the White/GMC WIM.
The 194 operates at a significantly lower wattage than the 1157, reflecting its role in a low-intensity marker application rather than a high-visibility signaling function.