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/InstallationLight Bulbs
WARNING
Do not replace the xenon fusion bulbs yourself:
Replacing the xenon fusion bulbs yourself is dangerous. Because the xenon fusion
bulbs require high voltage, you could receive an electric shock if the bulbs are
handled incorrectly. Consult an Authorized Mazda Dealer when the replaceme ...
Main Silencer
Purpose, Function
Reduces the exhaust noise.
Construction
The main silencer is installed to the vehicle rear, under the trunk compartment.
2WD
AWD
The main silencer consists of the filters, holder, set plates and stiffener.
...
Keyless Antenna [Keyless Entry System]
Purpose
Outputs a request signal and specifies the remote transmitter location.
Function
The keyless antennas output request signals based on the signals from the
start stop unit.
Construction, Operation
Request signals are output by the keyless antenna installed ...