Cadillac Catera front turn signal bulbs utilize 3457NA or 3357NA sizes, while rear turn signal bulbs use PY21W or 12496 sizes. The replacement chart covers 1997 to 2001 vehicle production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 3457NA bulb follows the ANSI standard used in the United States and Canada. It is a dual-filament T25 wedge bulb rated at 12V with a 27W main filament and a 7W secondary filament, and its natural amber glass produces a colored output without the need for an amber lens.
The Cadillac Catera front turn signal uses the 3457NA for model years 1997 and 1999-2001, making it the most consistently specified bulb across the front position in these specifications.
The 3357NA differs from the 3457NA in that it carries only a single filament rated at 27W, rather than the dual-filament configuration. Both share the T25 wedge form factor, ANSI standardization, natural amber glass, and 12V operation, which can create confusion during replacement.
The 1998 Cadillac Catera front turn signal is specified with the 3357NA rather than the 3457NA used in surrounding model years. Because the 3357NA is single-filament and the 3457NA is dual-filament, these two bulbs are not functionally interchangeable despite their physical similarities.
The PY21W bulb follows the ECE standard used in Europe and worldwide markets. It uses a BAU15s offset bayonet base, is rated at 12V and 21W, and produces amber light from a single filament. The offset pin configuration of the BAU15s base prevents installation of non-amber bulbs sharing a similar base style.
The Cadillac Catera rear turn signal uses the PY21W for model years 1999-2001. The BAU15s bayonet base is physically distinct from the wedge base of the ANSI-standard bulbs used in the front position, so the front and rear bulbs for those years are not interchangeable.
The 12496 is a Philips/Osram part number designation rather than an ANSI or ECE standard code. It is a halogen bulb rated at 12V and is specified for the Cadillac Catera rear turn signal in 1997-1998.
The rear turn signal position transitions from the 12496 in 1997-1998 to the PY21W in 1999-2001, meaning these two bulb types serve the same position across different model years but are distinct in their base type and wattage, and are not interchangeable with each other.
The natural amber glass construction of both the 3457NA and 3357NA means the amber color is produced by the bulb itself. Substituting a clear equivalent bulb of the same base type would alter the color output at the lens.
Across all five model years, the Cadillac Catera uses different bulb standards for the front and rear turn signal positions within the same model year, with ANSI-coded wedge bulbs at the front and either ECE or proprietary-coded bulbs at the rear.