Pontiac Grand Prix Back Up Light Bulb Size

Additional Notes

• The 1156 bulb is the most frequently specified size across the Pontiac Grand Prix backup light fitment data, appearing in model years 1962-1970 and 1973-1988, which represents the longest continuous stretch of any single bulb type in these specifications.
• The 1156 is a single-filament bulb rated at 12V and 21W, using a BA15s bayonet base. Its single-filament design means it serves one lighting function only, which is consistent with its use in a dedicated backup light application.
• The 3057 bulb is specified for the 1988-2004 Grand Prix across eight model years from 1989-1996, making it the second most recurring type in these specifications. It is a dual-filament T25 wedge bulb rated at 12V with a 27W high filament and a 7W low filament.
• Because the 3057 carries two filaments at different wattages, it is physically and electrically distinct from a single-filament replacement. Substituting a single-filament bulb in a socket wired for dual-filament operation would result in incomplete circuit function.
• The 2004 Pontiac Grand Prix uses the 3157, a dual-filament T25 wedge bulb rated at 12V, 27W/7W. Although the 3157 and 3057 share the same T25 wedge form and wattage ratings, they are not confirmed as interchangeable within these specifications, as each is listed for a distinct model year.
• The 2456 is a festoon-style bulb rated at 12V and is listed for the 1999-2000 and 2002-2003 model years. Festoon bulbs are cylindrical in form and seat by contact pressure at each end rather than through a bayonet or wedge base, which makes them physically incompatible with sockets designed for other base types.
• The 2356 uses a BAY15d bayonet base and is listed for the 1997 and 2001 model years. The BAY15d base is a dual-contact bayonet fitting, the same base type used by the 1157 bulb, though the two are not listed as interchangeable in these specifications.
• The 1157, specified for the 1971-1972 Grand Prix, is a dual-filament bulb with a BAY15d bayonet base rated at 12V, 21W/5W. Its wattage profile differs from the 2356, which shares the same base type but carries different electrical characteristics.
• The 889 is a single-filament halogen bulb rated at 12V and 37.5W, using a PGJ13 base. It is specified only for the 1988 Grand Prix and represents the sole halogen type across the entire range of specifications listed. Its PGJ13 base is mechanically distinct from all other base types present in these specifications.
• The 3156, specified for the 1998 Grand Prix, is a single-filament T25 wedge bulb rated at 12V and 27W. It shares the same T25 wedge housing as the 3057 and 3157 but differs in filament count, making it electrically distinct from those dual-filament types despite the physical similarity.