GMC K2500 Suburban Back Up Light Bulb Size

The GMC K2500 Suburban back up light utilizes 1156, 2356, 2456, and P21W bulb sizes for the rear illumination system. Data for the specified vehicle components covers the period from 1979 through 1999.

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
1997-1999	2456
1996	2356
1992-1995	2456
1979-1986	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, specialty application. 12V.	2456
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V.	2356
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The GMC K2500 Suburban uses three distinct bulb types across its model years for the back up light position: the 2456, 2356, and 1156.
The 1156 is the most historically established bulb in these specifications, fitted to the K2500 Suburban from 1979-1986. It is a single-filament bulb rated at 12V and 21W, using a BA15s bayonet base, and meets ANSI standards for the US and Canadian markets.
The 2456 is the most frequently specified bulb across these model years, covering 1992-1995 and 1997-1999. It is a festoon-type bulb rated at 12V, also conforming to ANSI standards for the US and Canada.
The 2356 appears exclusively in the 1996 GMC K2500 Suburban. It is a dual-filament bulb with a BAY15d bayonet base, rated at 12V, and carries ANSI certification for the US and Canadian markets.
The BAY15d base of the 2356 and the BA15s base of the 1156 are physically distinct bayonet fittings. The BAY15d base has offset pins to accommodate dual-filament operation, while the BA15s base uses symmetrical pins for single-filament use, making these two bulbs non-interchangeable.
The festoon form of the 2456 differs structurally from both bayonet-based bulbs in these specifications. Festoon bulbs mount by contact pressure at each end rather than by a base socket, which means the 2456 is not interchangeable with either the 1156 or the 2356.
The 1996 model year stands apart from adjacent years in these specifications, as it is the only year specifying the dual-filament 2356 rather than the 2456 used in surrounding model years.