GMC V1500 Suburban Back Up Light Bulb Size

The GMC V1500 Suburban back up light requires bulb size 1156 or P21W depending on the specific configuration. Available data for the bulb covers the range from 1987 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
1987-1991	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 GMC V1500 Suburban uses the 1156 bulb for the back up light across all listed model years, spanning 1987-1991.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical specifications are governed by a recognized North American standard shared across the US and Canada.
This bulb operates on a 12-volt electrical system and draws 21 watts, which is consistent with standard automotive reverse lighting applications.
The 1156 uses a BA15s bayonet base, a single-contact mount where the "s" denotes a single pin, distinguishing it from dual-contact bayonet variants.
The single-filament design of the 1156 means it serves one lighting function only, which in this application is the reverse light.
The BA15s base is not interchangeable with the BA15d base, as the latter has two offset pins for dual-filament bulbs. Substituting one for the other is not possible without a socket modification.