Mercury Grand Marquis Back Up Light Bulb Size

The Mercury Grand Marquis back up light utilizes unique bulb sizes 3156, 2356, 2456, P21W, and 1156 depending on the specific production period. Available data covers the range from 1975 to 2011.

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
2009-2011	3156
2008	2356
2006-2007	2456
2005	2356
2004	3156
2003	2356
2002	2456
2001	3156
1999-2000	2456
1998	3156
1995-1997	2456
1993-1994	3156
1990-1992	2356
1989	2456
1975-1988	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament wedge bulb (T25). 12V, 27W.	3156
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 Mercury Grand Marquis back up light specifications span model years 1975 through 2011, with three distinct bulb types appearing across that range: the 1156, 2356, 2456, and 3156.
The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W under the ANSI standard. It is the designated back up light bulb for the Grand Marquis from 1975-1988.
The 3156 is a single-filament wedge bulb in a T25 form factor, rated at 12V and 27W under the ANSI standard. It is specified for the Grand Marquis in 1993-1994, 1998, 2001, 2004, and 2009-2011.
The 2356 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V under the ANSI standard. It is specified for the Grand Marquis in 1990-1992, 2003, 2005, and 2008.
The 2456 is a festoon-style bulb for specialty applications, rated at 12V under the ANSI standard. It is specified for the Grand Marquis in 1989, 1995-1997, 1999-2000, 2002, and 2006-2007.
The 1156 and 3156 are both single-filament bulbs, but they use different base types. The 1156 uses a BA15s bayonet base while the 3156 uses a wedge base, making them physically non-interchangeable despite sharing a single-filament design.
The 2356 uses a BAY15d bayonet base, which is a dual-contact base. This base type differs from the BA15s base of the 1156, so those two bulbs are not interchangeable even though both use bayonet-style mounting.
The 2456 festoon bulb is mechanically distinct from the bayonet-base and wedge-base types also found in these specifications, as festoon bulbs are held in place by end caps rather than a base socket.
All four bulb types in these specifications conform to ANSI standards applicable in both the United States and Canada, indicating standardized electrical and physical tolerances across the range.
The back up light bulb specification for the Grand Marquis changed multiple times across consecutive model years, meaning the correct bulb size is year-specific and cross-year substitution is not supported by these specifications.