BMW 135i Back Up Light Bulb Size

The BMW 135i back up light requires a bulb size of 921 for the rear lighting assembly. Available data for the specified vehicle covers the range from 2008 through 2013.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2008-2013	921

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921

Other Locations

Additional Notes

The BMW 135i uses the 921 bulb size for the back up light across all listed model years, spanning 2008-2013.
The 921 is classified as a T15 wedge-type bulb, meaning it connects directly into a socket without a separate base or pins, relying on two angled metal tabs on the glass envelope to make electrical contact.
The 921 operates at 12 volts and 16 watts, which places it in the standard low-wattage range typical of reverse lighting applications in passenger vehicles.
The 921 bulb conforms to ANSI standards, indicating it meets the dimensional and performance specifications established for the North American market, covering both the United States and Canada.
The T15 designation refers to the bulb's tubular shape, with the number 15 representing a width of 15 eighths of an inch, a sizing convention used in the ANSI bulb classification system.
Because the 921 is a wedge-type bulb, it is not interchangeable with bayonet or single-contact base bulbs, even when voltage and wattage ratings are otherwise similar.