1. Disconnect the negative battery cable..
2. Remove the front bumper..
3. Remove the horn..
4. Apply battery positive voltage and connect the ground as shown in the figure and verify the horn beeper sound operation.

If the beep sound cannot be verified, replace the horn.
Horn
Horn Removal/InstallationElectrical System
Electrical Parts
Battery cable
Before disconnecting connectors or removing electrical parts, disconnect
the negative battery cable.
Wiring Harness
To remove the wiring harness from the clip in the engine room, pry up the
hook of the clip using a flathead screwdriver. ...
Parking Support Brake function (pedestrians rear of the vehicle)
The Subaru Solterra is equipped with a rear camera-based detection
system capable of identifying pedestrians behind the vehicle while reversing. When
a pedestrian is detected and the system determines that collision risk is elevated,
an audible warning is issued. If the danger becomes critical ...
Fuel Injector Removal/Installation [Mzr 2.0, Mzr 2.5]
WARNING:
Fuel is very flammable liquid. If fuel spills or leaks from the pressurized
fuel system, it will cause serious injury or death and facility breakage. Fuel
can also irritate skin and eyes. To prevent this, always complete the “Fuel
Line Safety Procedure”, while referring ...