Hyundai Sonata Brake Bulb Size

Additional Notes

• The 2357 bulb is the most frequently specified brake bulb size across the Hyundai Sonata's history, appearing across model years spanning 1997-2001, 2006-2019, and isolated years in the 1990s. It is a dual-filament ANSI-standard bulb with a BAY15d bayonet base rated at 12V and 26.9W/8W, making it a higher-output variant of the 1157.
• The 1157 bulb shares the same BAY15d bayonet base and dual-filament design as the 2357 but operates at a lower wattage of 21W/5W. Both bulbs use the same base type, though their differing wattage ratings mean they are not direct equivalents despite their physical similarity.
• The H21W is an ECE-standard single-filament bulb with a BAY9s base, rated at 12V and 21W. Its base type differs from the BAY15d used by the 1157 and 2357, meaning it is not interchangeable with those bulbs even where wattage values overlap.
• For the 2021-2022 Hyundai Sonata, the brake bulb specification depends on the vehicle's country of assembly. US-built units require the H21W, while Korea-built units require the 1157. These two bulbs use different base types and are not interchangeable with each other.
• The 2016-2019 Sonata brake bulb specification for the 2357 carries a conditional note restricting it to vehicles equipped with halogen capsule headlamps, indicating that trim or equipment level affects the correct bulb fitment.
• The 921 is a single-filament wedge-type bulb in the T15 form factor, rated at 12V and 16W under the ANSI standard. It is specified exclusively for the Center High Mount Stop Light across multiple Sonata model years and is physically and electrically distinct from the bayonet-base bulbs used in the main brake light positions.
• The P21W is an ECE-standard single-filament bulb with a BA15s bayonet base, rated at 12V and 21W. It is specified for the Center High Mount Stop Light on the 1999-2001 Sonata, and its BA15s base differs from the BAY15d base of the 1157 and 2357, making cross-substitution incompatible.
• The 921 and P21W are both single-filament bulbs rated at 12V and 21W or 16W respectively, yet they use entirely different base types, the wedge T15 format versus the BA15s bayonet, and are therefore not interchangeable despite serving the same Center High Mount Stop Light position across different model years.