Cadillac XT5 Map Light Bulb Size

The Cadillac XT5 map light requires bulb size 6428 or DE3021 depending on the specific configuration of the vehicle. Data for the lighting components covers the range from 2017 to 2019.

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
2019	6428
2018	DE3021
2017	6428

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 36mm length, SV8.5 base. 12V, 5W.	6428
ANSI standard (US & Canada). Festoon bulb, 31mm length, end-cap contacts. 12V.	DE3021

Other Locations

Additional Notes

The 6428 is a festoon-type bulb rated at 12 volts and 5 watts, with a 36mm length and an SV8.5 base. It conforms to ANSI standards applicable in the US and Canada.
The DE3021 is also a festoon-type bulb rated at 12 volts, with a 31mm length and end-cap contacts. It likewise conforms to ANSI standards applicable in the US and Canada.
Festoon bulbs are cylindrical lamps that mount between two contact points at either end, making physical length a critical factor in fitment. The 6428 and DE3021 differ in length by 5mm, which means they are not interchangeable despite both being festoon types.
The Cadillac XT5 uses the 6428 bulb for the map light in the 2017 and 2019 model years, while the 2018 model year uses the DE3021 instead.
The SV8.5 base on the 6428 refers to a specific festoon socket size, whereas the DE3021 uses bare end-cap contacts without a defined socket base designation, reflecting a different mounting interface between the two bulbs.