Complaint/Problem	Possible cause	Remedy/Test step
Entire radio (A2) not functioning.	Power supply: Radio (A2)	23 1.0
No display in display window of radio (A2)	Power supply: Radio (A2)	23 1.0
Cassette player functions in radio (A2) not working	Power supply: Radio (A2)	23 1.0
Entire CD operation not functioning.	Power supply radio (A2), CD changer (A2/6)	23 1.0 , 2.0 or 3.0
Left front loudspeaker not operating.	Radio (A2), loudspeaker	23 4.0
Right front loudspeaker not operating	Radio (A2), loudspeaker	23 5.0
Left rear loudspeaker not operating	Radio (A2), loudspeaker	23 6.0
Right rear loudspeaker not operating	Radio (A2), loudspeaker	23 7.0
Radio interference	Radio (A2), Antenna	23 8.0
Poor radio reception	Radio (A2), antenna, Reception area	23 9.0
Automatic antenna (M11) not operating	Radio (A2), automatic antenna (M11)	23 10.0
Speed-sensitive volume control not operating	Radio (A2), vehicle speed signal (except model 163)	23 11.0
Radio illumination not operating	Radio (A2)	23 12.0
Radio mute switching when using telephone not operating	Radio (A2), cellular telephone system	23 13.0

Complaint/Problem/DTC	Possible cause	Notes	Test step/Remedy 1)
	Radio: Internal fault		Replace radio
	Radio: Low voltage		23 3.0
	Radio: High voltage		2 3 3.0
	Radio: CAN B fault		Check CAN data bus
	Radio: Automatic antenna switching circuit		Check antenna system (ATS)
	Radio: Cassette player or cassette faulty		Check cassette Replace radio
	Radio: Front flap end switch - locking Front flap end switch - openning		Replace radio Replace radio
	Radio: Internal fault CAN data bus failure		Replace radio Check CAN data bus
	Radio: D2B Data transfer faulty		Check connections Check fiber optics
	Radio: Data transfer between radio and preceding D2B component		Check connections Check fiber optics
	Radio: D2B Data transfer faulty		Check connections Check fiber optics
	Radio: D2B initialization fault		Reconfigure the D2B system, refer to HHT
	Radio: D2B initialization fault		Reconfigure the D2B system, refer to HHT
	Radio: D2B components not recognized (By-pass mode)		Check all D2B components, replace if necessary
	Radio: EEPROM defect		Replace radio
	Radio: RAM defect		Replace radio
	Radio: One or more buttons stuck		Press and test all buttons several times
	Radio: Low voltage		23 3.0
	Radio: Interal fault		Replace radio
	Radio: D2B Wake-up circuit - +		Check circuit
	Radio: CAN bus faulty		Check CAN data bus
	Radio: Nominal - actual values of the D2B- rings different		Reconfigure the entire D2B system, refer to HHT
	Radio: Scan function faulty (antenna connection)		Check antenna system (ATS)
	Radio: Cassette player or cassette faulty		Check cassette Replace radio

1) Observe Preparation for Test, see 22 .