The White/GMC WHL features front side marker bulbs in 1157 size and rear side marker bulbs in 194 size. The replacement chart covers 1988 to 1995 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 WHL 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 meets ANSI standards for use in the United States and Canada.
The BAY15d bayonet base features offset pins, which physically prevents substitution with single-filament bayonet bulbs that share a similar base profile but differ in pin alignment.
The rear side marker position on the White/GMC WHL takes the 194 bulb across the same 1988-1995 model range.
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 of the 194 bulb is not compatible with the BAY15d bayonet socket used by the 1157, meaning the front and rear side marker sockets are physically distinct and the two bulb types are not interchangeable with each other.
The significant wattage difference between the 1157 (21W/5W dual-filament) and the 194 (3.78W single-filament) reflects their different functional roles, with the higher-output 1157 suited to a position that may serve a signaling function in addition to marking.