GMC Sonoma Back Up Light Bulb Size

The GMC Sonoma back up light requires bulb sizes 3057, P21W, 1156, and 2057 depending on the specific vehicle configuration. Available data for the bulb sizes covers the range from 1991 to 2004.

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
1998-2004	3057
1994-1997	1156
1993	2057
1991-1992	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament wedge bulb (T25). 12V, 27W/7W.	3057
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. Brighter variant of 1157. 12V, 26.9W/8W.	2057

Other Locations

Additional Notes

The GMC Sonoma backup light specifications cover model years 1991 through 2004, with three distinct bulb types used across that span: the 3057, the 1156, and the 2057.
The 3057 is the most frequently specified bulb in these records, appearing across the 1998-2004 model years of the GMC Sonoma.
The 3057 is a dual-filament T25 wedge bulb rated at 12V with a 27W primary filament and a 7W secondary filament, conforming to ANSI standards for the US and Canada.
The 1156 is the second most common bulb in these specifications, covering the 1991-1996 model years, with the exception of 1993.
The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W, and also conforms to ANSI standards for the US and Canada.
The 2057 is specified exclusively for the 1993 GMC Sonoma. It is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 26.9W primary filament and an 8W secondary filament.
The 1156 and 2057 both use bayonet-style bases, but they are not interchangeable. The 1156 uses a BA15s single-contact base, while the 2057 uses a BAY15d dual-contact base with offset pins.
The 3057 uses a wedge-style base rather than a bayonet base, making it physically incompatible with sockets designed for the 1156 or 2057 without modification.
Although the 2057 is described as a brighter variant of the 1157, the 1157 itself is not specified for any model year of the Sonoma in these records.
All three bulb types in these specifications operate at 12V, which is consistent with standard automotive electrical systems.