White/GMC WHS Back Up Light Bulb Size

The White/GMC WHS back up light requires a bulb size of 1156 for the rear lighting assembly. Data for the specified component covers the range from 1988 to 1991.

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
1988-1991	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 WHS uses the 1156 bulb for its back up light across the 1988-1991 model years.
The 1156 is an ANSI-standardized bulb type, meaning its specifications are governed by a recognized North American standard applicable 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 1156 is a single-filament bulb, meaning it serves one lighting function only, as opposed to dual-filament types that can handle two functions such as braking and running lights simultaneously.
The 1156 uses a BA15s bayonet base, where "BA15s" denotes a bayonet cap with a 15mm base width and a single contact pin, which determines physical fitment into the socket.
The single-contact BA15s base of the 1156 is not interchangeable with the BA15d base found on dual-filament bulbs such as the 1157, despite the two types sharing a similar physical appearance and base width.