GMC C2500 Suburban Back Up Light Bulb Size

The GMC C2500 Suburban back up light utilizes 1156, 2356, 2456, and P21W bulb sizes. Available information covers the range from 1979 through 1999 for the specified vehicle components.

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
1999	2356
1996-1998	2456
1995	2356
1992-1994	2456
1979-1986	1156

Bulb Specifications

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

Other Locations

Additional Notes

The GMC C2500 Suburban uses three distinct back up light bulb types across its model years: the 1156, 2356, and 2456.
The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W under the ANSI standard applicable in the US and Canada. It was the back up light bulb for the C2500 Suburban from 1979-1986.
The 2456 is a festoon-style bulb intended for specialty applications, operating at 12V under the same ANSI standard. It served as the back up light bulb across the 1992-1994 and 1996-1998 model years.
The 2356 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V under the ANSI standard for the US and Canada. It was specified for the 1995 and 1999 model years.
The BAY15d base of the 2356 and the BA15s base of the 1156 are physically distinct bayonet fittings. The BAY15d has offset pins to accommodate dual-filament wiring, while the BA15s has a single-contact design, making these two bulbs non-interchangeable.
The 2456 festoon bulb uses a cylindrical form factor held in place by end caps rather than a bayonet base, which means it is physically incompatible with the socket types used by either the 1156 or the 2356.
The 2356 is a dual-filament bulb, though the back up light function on the GMC C2500 Suburban is a single-function circuit. Only one filament would be engaged in this application.
The 1995 model year uses the 2356, while the adjacent 1994 and 1996 model years use the 2456, indicating that the two bulb types are not interchangeable between those years despite the similar voltage rating.