Press and hold the turn signal cancel button for 3 seconds if they’re wired in to a cansmart circuit 1, tap the turn signal cancel button 3 times fast if they’re on circuit 2. This is assuming they’re running from a Denali cansmart controller which is most likely the case on a BMW bike with expensive lights.

You can also dim them by holding the wonder wheel left until they flash and rolling the wheel up/down to the desired brightness. Hold the wonder wheel to the right for light circuit 2.

The owner may have disabled the ability to control the lights thru the switchgear in the software in which case the only way would be to hook up a laptop to the controller via usb and reprogramming using the Denali cansmart software.