Jeep Grand Cherokee Back Up Light Bulb Size

Additional Notes

• The 921 bulb is the most frequently specified size across the Jeep Grand Cherokee backup light fitments. It is an ANSI-standard T15 wedge bulb rated at 12V and 16W, used in single-filament applications.
• The 7440 is a T20 single-filament wedge bulb rated at 12V and 21W. In the 2021 Grand Cherokee, it is designated for the in-body backup light position, while the 921 fills the in-liftgate position, meaning the 2021 model year uses two different bulb sizes simultaneously.
• For the 2011-2020 Grand Cherokee, the inner and outer backup light positions take different bulb sizes. The inner position uses the 921, and the outer position uses the 7440.
• The 3157 and 3057 are both dual-filament T25 wedge bulbs rated at 12V with a 27W/7W output. Their dual-filament design means they are not directly interchangeable with the single-filament 921 or 7440 bulbs used in other Grand Cherokee model years.
• The 3157 was specified for the 1999-2006 Grand Cherokee backup lights, while the 3057 was used in 1997-1998. Although both share the same T25 form and wattage ratings, they have different internal filament configurations and are not considered interchangeable with each other.
• The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W. It was specified for the 1993-1996 Grand Cherokee, and its bayonet mounting base makes it physically distinct from the wedge-base bulbs used in all later model years.
• The shift from the bayonet-base 1156 to the wedge-base 3057 between the 1996 and 1997 model years represents a socket-type change, meaning bulbs from those respective periods are not physically interchangeable.
• The 921 and 7440 are both wedge-base bulbs, but they differ in body size (T15 versus T20) and wattage (16W versus 21W). Substituting one for the other is not supported by the specifications, as each is assigned to a distinct position.