Power supply +15

Fig 1: Identifying Xenon Headlamps Communication Diagram - Power Supply

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Identifying Xenon Headlamps Circuit Diagram - Power Supply

Courtesy of SAAB-SCANIA OF AMERICA, INC.

From fuse 21 in dashboard fuse box to headlamp, pin 10.

This power supply keeps the control module awake in case of a break in the main voltage supply.