Hyundai Sonata Turn Signal Bulb Size

Additional Notes

• The 2357NA is the most frequently specified bulb across the Hyundai Sonata turn signal data, appearing as the front turn signal bulb from 1989 through 2019, with the exception of 2021. It is a dual-filament ANSI-standard bulb rated at 12V with a high-beam filament drawing 26.9W and a low-beam filament drawing 8W, fitted with a BAY15d bayonet base and natural amber glass coating.
• The 1156NA is the most commonly listed rear turn signal bulb, covering the 2002-2019 model years for that position. It is a single-filament ANSI-standard bulb with a BA15s bayonet base and natural amber glass, rated at 12V and 21W. Its single-filament design contrasts with the dual-filament 2357NA used at the front during the same period.
• The Hyundai Sonata (2021) uses different bulb standards at the front and rear turn signal positions simultaneously. The front requires a PY21W, which follows the ECE standard used in Europe and worldwide, while the rear requires a P21/5W, also an ECE-standard bulb. This makes the 2021 model year notable for its exclusive use of ECE-type bulbs in both turn signal positions.
• The PY21W, specified for the 2021 front turn signal, uses a BAU15s bayonet base. This base has an offset pin arrangement that physically prevents substitution with bulbs using the standard BA15s or BAY15d bases, making cross-substitution with ANSI-type bulbs mechanically incompatible.
• The P21/5W, used in the 2021-2022 rear turn signal positions, shares the BAY15d bayonet base with the ANSI-standard 2357 and 2357NA bulbs. However, P21/5W follows ECE ratings at 21W/5W, and direct substitution with ANSI dual-filament bulbs of the same base type is not confirmed by the specifications.
• The 2357 and 1156 bulbs, listed for rear turn signal positions in earlier model years, are the standard (non-amber) versions of the 2357NA and 1156NA respectively. The 2357NA and 1156NA variants achieve their amber output through natural amber glass rather than a clear envelope, which is a distinction relevant to compliance with regulations that require amber turn signal light output.
• The 921 bulb, specified for the 2023-2024 rear turn signal, uses a wedge-type T15 base rather than a bayonet fitting. This base type is physically incompatible with the BA15s and BAY15d bayonet sockets used by all other bulbs listed in these specifications, meaning the 2023-2024 rear turn signal housing represents a distinct socket design from earlier model years.
• The rear turn signal position of the Hyundai Sonata reflects three separate base types across its model year range: the BA15s single-contact bayonet base (1156, 1156NA), the BAY15d dual-contact bayonet base (2357, P21/5W), and the T15 wedge base (921). These base types are mutually incompatible, and bulb selection must correspond to the specific socket present in the vehicle for a given model year.