GMC Sierra Back Up Light Bulb Size

GMC Sierra back up light bulbs utilize 921, 1156, and 3047 bulb sizes, with outer back up light positions requiring 1156 or 921 sizes. The replacement chart covers vehicle production years from 1999 through 2024.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Back Up Light

If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.

Years	US Type	EU Type	Shop
2023-2024	1156 (1500 only)	P21W	Check Price
2023-2024	921 (3500 HD only)	W16W	Check Price
2022	921	W16W	Check Price
2021	921 (With Fleetside)	W16W	Check Price
2021	1156 (Without Fleetside)	P21W	Check Price
2014-2020	921	W16W	Check Price
2007-2013	3047	3047	Check Price
2000-2006	3157	P27/7W	Check Price
1999	2456 (1500 only)	2456	Check Price
1999	921 (2500/3500 only)	W16W	Check Price

Outer Back Up Light

Years	US Type	EU Type	Shop
2019	1156 (With Chassis Cab, 3500 HD only)	P21W	Check Price
2019	921 (Without Chassis Cab (ZW9), 3500 HD only)	W16W	Check Price
2017-2018	1156 (1500 only)	P21W	Check Price
	1156 (With Chassis Cab, 3500 HD only)	P21W	Check Price
	921 (Without Chassis Cab (ZW9), 3500 HD only)	W16W	Check Price

Bulb Specifications

Description	Type	Shop
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156	Check Price
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W	Check Price
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921	Check Price
ANSI standard (US & Canada). Single-filament wedge bulb (T25). 12V, 27W.	3047	Check Price
ANSI standard (US & Canada). Dual-filament wedge bulb (T25). 12V, 27W/7W.	3157	Check Price
ANSI standard (US & Canada). Festoon bulb, specialty application. 12V.	2456	Check Price

Other Locations

Additional Notes

The 921 bulb is a T15 wedge type rated at 12V and 16W. It is the most frequently specified backup light bulb across the GMC Sierra range, appearing in model years 2014-2024 as well as in the 1999 Sierra 2500/3500.
The 1156 bulb uses a BA15s single-contact bayonet base and is rated at 12V and 21W. It is a single-filament type, making it distinct from dual-filament bulbs that serve multiple lighting functions from one housing.
The 3047 bulb is a single-filament T25 wedge type rated at 12V and 27W. It was the specified backup light bulb for the Sierra across the 2007-2013 model years.
The 3157 bulb is a dual-filament T25 wedge type rated at 12V, with filaments drawing 27W and 7W respectively. Despite its dual-filament construction, it served as the backup light bulb on the Sierra from 2000-2006.
The 3047 and 3157 share the same T25 wedge form factor and identical voltage ratings, but the 3157 carries a second filament. This structural difference means the two bulbs are not interchangeable, even though they occupy the same bulb family.
The 2456 is a festoon-type bulb rated at 12V and is designated for specialty applications. It was specified exclusively for the 1999 GMC Sierra 1500 backup light, while the 1999 Sierra 2500/3500 used the 921 instead.
On the 2021 Sierra, backup light bulb fitment is split by bed configuration. The Fleetside body style takes the 921, while non-Fleetside configurations take the 1156, which operates at a higher wattage of 21W.
For the 2023-2024 Sierra, the 1500 trim uses the 1156 bulb while the 3500 HD uses the 921, indicating that bulb fitment varies by sub-model within the same production year.
The outer backup light on the 2017-2019 Sierra 3500 HD is split between two bulb types depending on cab configuration. The Chassis Cab variant takes the 1156, while the non-Chassis Cab variant with option code ZW9 takes the 921.
All five bulb types specified across the Sierra lineup conform to ANSI standards applicable in both the United States and Canada, and all operate on a 12V electrical system.