DPX500BT/DPX300U 20. Troubleshooting guide 20-2. Operation/wiring error20-2. Operation/wiring errorWhat might seem to be a malfunction in your unit may just be the result of a slightoperation error or a wiring error. Before calling for service, first check the followingtable for possible problems.GeneralThe key beep does not soundThe Preout jack is in use.The key beep cannot be output from the Preout jack.Sound cannot be heard.Adjust the volume to the optimum level.Check the cords and connections.Tuner sourceRadio reception is poor.The car antenna is not extended.Pull the antenna out all the way.Disc sourceThe specified disc does not play, but another one plays instead.The specified CD is quite dirty.Clean the CD with reference to <9-10. Handling discs>.The disc is severely scratched.Try another disc instead.Disc cannot be ejected.The unit is malfunctioning for some reason.Press and hold [ ] to forcibly eject the disc. Be careful not to drop the discwhen it is ejected. If this does not solve the problem, reset the unit.Audio file sourceThe sound skips when an Audio file is being played.The media is scratched or dirty.Clean the CD with reference to <9-10. Handling discs>.The recording condition is bad.Play the media again or use another media.iHeartRadio sourceStation cannot be selected.If "Explicit Content" in [Account Settings] is checked in the web version ofiHeartRADIO, some stations become unavailable.Bluetooth sourceThe hands-free talk volume is low.The hands-free talk volume can be adjusted independently.Adjust it during hands-free talk. "MIC GAIN" of <17-5. Bluetooth detail setting>.No beep is heard at reception of an incoming call.