Honda Civic Back Up Light Bulb Size

Additional Notes

• The 1156 bulb is the most frequently specified backup light bulb across the Honda Civic model years listed, appearing in every entry from 1973 through 1991, with the exception of 1984 and 1985.
• The 1156 operates at 12 volts and draws 21 watts, making it a higher-wattage option compared to the 921 bulb also referenced in these specifications.
• The 1156 uses a BA15s bayonet base, which is a single-contact bayonet mount. This base type is not interchangeable with wedge-style sockets.
• The 921 is specified for the 2024 Honda Civic backup light. It is a T15 wedge bulb rated at 12 volts and 16 watts.
• The T15 wedge base of the 921 bulb seats by friction fit into a wedge socket, a fundamentally different mounting method than the bayonet base of the 1156. The two bulb types are not interchangeable despite sharing the same 12-volt operating voltage.
• Both the 921 and 1156 conform to ANSI standards applicable in the United States and Canada, meaning their physical and electrical characteristics follow a standardized specification recognized across those markets.
• The 1156 is a single-filament bulb, which means it serves one lighting function per socket. In backup light applications, this single filament is dedicated solely to the reverse lighting circuit.
• The wattage difference between the 1156 at 21 watts and the 921 at 16 watts reflects a reduction in power draw in the more recent Civic specification, consistent with a general industry shift toward lower-wattage or alternative lighting technologies in newer vehicles.