Inspection Procedure 7: No Sound is Output from the Wireless Headphone.
DIAGNOSIS PROCEDURE
STEP 1. Speaker check
When the speaker sound is set to the rear monitor output, check whether the rear monitor sound is output from the speakers.
Q.
Is the check result normal?
Go to Step 2.
Refer to Inspection Procedure 6 "The rear monitor sound is not output from the speaker" 
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STEP 2. Wireless headphone battery check
Replace the wireless headphone battery, and check the wireless headphone sound.
Q.
Is the check result normal?
Go to Step 3.
Repair the connector concerned.
STEP 3. Replace the wireless headphone temporarily, and check the trouble symptom.
Replace the wireless headphone temporarily, and check if sound is output from the wireless headphone.
Q.
Is the check result normal?
Replace the wireless headphone.
Replace the rear monitor.