The GMC C2500 Suburban front side marker uses 194 or 168 bulb sizes while the rear side marker requires a 194 bulb size. The replacement chart covers 1979 to 1999 model 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 two bulb types specified across the GMC C2500 Suburban side marker positions are the 194 and 168, both of which are ANSI-standardized miniature wedge bulbs sharing the T10 form factor and a 12-volt operating voltage.
Although the 194 and 168 share the same T10 wedge base and voltage rating, they differ in wattage. The 194 draws 3.78 watts, while the 168 draws 4.9 watts, making them electrically distinct despite their physical similarity.
Because the 194 and 168 share the T10 wedge base, one may physically seat in a socket intended for the other. However, the wattage difference means they are not interchangeable without affecting the electrical load on that circuit.
The front side marker position on the GMC C2500 Suburban used the 168 bulb from 1979-1986 and transitioned to the 194 bulb from 1992-1999.
The rear side marker position on the GMC C2500 Suburban used the 194 bulb across all listed model years, spanning 1979 through 1999.
From 1992-1999, the front and rear side marker positions on the C2500 Suburban share the same 194 bulb specification, meaning a single bulb type serves both locations during those years.
During the 1979-1986 model years, the front side marker required the higher-wattage 168 bulb, while the rear side marker used the lower-wattage 194, meaning the two positions called for different bulbs at the same time.
Both the 194 and 168 carry ANSI standardization recognized in both the United States and Canada, placing them within a widely distributed bulb classification system used across many vehicle makes.