The Acura MDX back up light utilizes 7440 and 921 bulb sizes for the rear illumination system. Data for the specific components covers the range from 2001 to 2020.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Acura MDX back up light bulb specifications cover model years 2001 through 2020, with two distinct bulb types used across that span: the 921 and the 7440.
The 921 bulb is a T15 wedge type rated at 12V and 16W, conforming to ANSI standards applicable in the US and Canada.
The 7440 bulb is a T20 single-filament wedge type rated at 12V and 21W, also conforming to ANSI standards for the US and Canada. Its higher wattage means it produces more light output than the 921.
The Acura MDX (2001-2013) uses the 921 bulb for the back up light, while the 2014-2020 model years use the 7440.
Although both the 921 and 7440 are wedge-type bulbs, they belong to different size classifications, T15 and T20 respectively, and are not interchangeable despite their similar form factor.
The wattage difference between the two bulbs, 16W for the 921 versus 21W for the 7440, means substituting one for the other could affect circuit load and light output.
The 2017-2018 MDX carries a separate outer back up light position that also uses the 7440 bulb, indicating that those model years have more than one back up light bulb position.
The single-filament design of the 7440 means it serves one lighting function only, as opposed to dual-filament bulbs that can serve two functions within a single housing.