1. Disconnect the negative battery cable..
2. Remove the following parts:
a. Trunk end trim.
b. Rear scuff plate (RH).
c. Trunk side trim (RH).
d. Theft-deterrent horn.
3. Apply battery positive voltage to horn terminal A, and connect the horn retaining bolt to ground as shown in the figure, and then verify that the horn sounds.

If the horn does not sound, replace the horn.
Remote Transmitter Battery Voltage Inspection
Theft Deterrent Horn Removal/InstallationUltra High Tension Steel [Construction]
Characteristics of Ultra High-Tensile Steel Plates
Ultra high-tensile steel plates have enhanced tensile strength compared to
previous high-tensile steel plates.
Because the strength is maintained even though the plates are thin-walled,
the ultra high-tensile steel plates ar ...
Manual Transaxle [C66 M R]
Purpose, Function
The MTX converts the drive force (speed, torque, rotation direction) input
from the engine according to the shift lever operation inside the vehicle.
Construction
Operation
...
Liftgate Latch Switch
Purpose, Function
The switch turns on/off in conjunction with the rotation of the latch lever,
and it detects the open/closed condition of the liftgate by the voltage value
which is changed by the rear body control module (RBCM).
Construction
The switch is turned on/off by ...