White/GMC WAH Back Up Light Bulb Size

The White/GMC WAH back up light utilizes a 1156 bulb size for illumination purposes. Data for the specified component covers the period from 1990 through 1995.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1990-1995	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The White/GMC WAH specifies the 1156 bulb for the back up light across the 1990-1995 model years.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical characteristics conform to a defined North American standard recognized in both the United States and Canada.
The 1156 operates on a 12-volt electrical system and draws 21 watts, which is typical of incandescent automotive bulbs used in signaling and reversing light applications.
The bulb uses a BA15s bayonet base, a single-contact fitting where the "s" designation indicates a single pin offset to one side, which controls insertion orientation.
Because the 1156 is a single-filament bulb, it serves one dedicated lighting function, distinguishing it from dual-filament variants such as the 1157, which handles two functions within one housing.
The BA15s base is not interchangeable with the BA15d base, as the latter features two contact pins and is designed for dual-filament bulbs; substituting one for the other is not possible without modification.