Hummer H1 Back Up Light Bulb Size

The Hummer H1 back up light requires bulb size 1156 or P21W depending on the specific version of the vehicle. Data for the bulb specifications covers the range from 2002 through 2006.

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
2006	1156
2002-2004	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

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Additional Notes

The Hummer H1 uses the 1156 bulb for its back up light across the 2002-2004 and 2006 model years.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical specifications are governed by a recognized North American standard shared across the US and Canada.
The 1156 operates at 12 volts and 21 watts, which places it in the range typical of standard automotive signaling and reversing applications.
The bulb uses a BA15s bayonet base, a single-contact mount where the "s" denotes a single pin, distinguishing it from the dual-contact BA15d variant with which it is not interchangeable.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, as opposed to dual-filament types that handle two functions such as braking and running light simultaneously.
The BA15s bayonet base requires a quarter-turn insertion method, where the bulb is pressed into the socket and rotated to lock in place.
Because the 1156 and the visually similar 1157 share the same BA15 base family but differ in filament count and pin configuration, the two types are not interchangeable in the Hummer H1 back up light socket.