Volkswagen Passat Back Up Light Bulb Size

Additional Notes

• The Volkswagen Passat back up light specifications cover model years 1990 through 2021 and reference two distinct bulb types: the 921 and the P21W.
• The 921 is an ANSI-standard wedge bulb of the T15 type, rated at 12 volts and 16 watts, and is the designated back up light bulb for the Passat across model years 2012-2021.
• The P21W is an ECE-standard single-filament signalling bulb with a BA15s bayonet base, rated at 12 volts and 21 watts, and is specified for the Passat across model years 1990-2011.
• The ANSI standard governs bulb specifications primarily in the United States and Canada, while the ECE standard applies in Europe and other markets worldwide, reflecting the different regulatory frameworks behind each bulb type.
• The 921 and P21W are not interchangeable. The 921 uses a wedge base, while the P21W uses a BA15s bayonet base, meaning the two bulbs require physically different socket types.
• Although both bulbs operate at 12 volts, the P21W is rated at 21 watts compared to the 921 at 16 watts, representing a difference in power consumption between the two fitments.
• The BA15s designation on the P21W indicates a single-contact bayonet cap with a 15mm base width, a base type commonly associated with European automotive lighting standards.
• The T15 designation on the 921 refers to the wedge base form factor, which is retained in the socket by friction rather than by a locking mechanism such as a bayonet fitting.