Mobile phone and VCS: Poor call quality and/
or voice control misunderstands commands
Topic number

LI82.70-P-064726

Version

5

Function group

82.70 Telephone, Voice-control-system(VCS)

Date

01-08-2020

Validity

Model series 213, 238, 177, 167, 118, 247
Model series 253 Facelift

Reason for change

Validity expanded, cause and remedy adapted

Reason for block

Complaint:

The following complaints may be noted by the customer:
- During a phone call, the called party may have difficulty understanding the drivr/passenger, or interference/background noises are audible to the called party during a call
- Voice control does not understand or misunderstands spoken commands
- Voice control does not activate with the "Hey Mercedes" keyword (NTG6 equipped vehicles only)

Cause:

- Installation of microphones (B25/20 or B25/21) in the headliner.
- Wiring between microphone (B25/20 or B25/21) and head unit (A26/17) --> See PE82.85-P-2110-97DBA (213 model series) or PE82.85-P-2110-97IBA (177 model series) for reference
- Debris inside the microphone housing

Remedy:

Before proceeding process any relevant fault codes and perform the recommended guided tests per XENTRY diagnosis.
Identify which microphone is affected (if no DTCs are present):
- Perform a bluetooth call on a mobile device from both passenger and driver's seats and note any difference in call
quality as noted by the external "called" party
- On NTG6 vehicles with E420.5 or newer MBUX multimedia system (A26/17) software activate the voice control system (VCS) using "Hey Mercedes" and change the climate control setting by stating "I'm hot" or "I'm cold". This will
prompt the climate control temperature setting to go up or down on the side of the vehicle where you are seated. Also
the ambient lighting will change color (red or blue dependings on temperature change) on that side of the vehicle and
the head unit display will have a graphical indicator noting which side the function was activated from (see attached).
The success of this test is a good indicator of microphone functionality.
- In some instances both microphones may be affected
Check installation of both microphones (B25/20 and B25/21):
- Check for and remove any foreign debris located between the microphone and the microphone cover
- Reinstall microphone into headliner ensuring that microphone cover is fully seated onto the microphone housing.
You should feel it "click" once it is seated properly
Check the wiring between the microphones (B25/20 or B25/21), the intermediate microphone electrical connector in
the headliner, and the head unit (A26/17)
01-08-2020 5:09 PM
© Copyright Mercedes-Benz AG

CTENORE

Page 1/4

- Check connectors to ensure they are fully seated and inspect connectors, wiring, and pins for damage
- Check continuity from the microphone to microphone electrical connector and from the electrical connector to the
head unit
- Ensure that pins are wired correctly, i.e. ensure the signal and ground wires are not switched in the connector
If the complaint is still present after the test steps listed above have been performed, replace the affected
microphone(s).

Attachments
File

Description

MBUX VCS directionality cue.jpg

Screenshot of MBUX VCS directional graphic (yellow shading at the top left of display)

Symptoms
Communication/information / Communication / Voice control system VCS / Input is not understood
Communication/information / Communication / Mobile phone / Telephone / Poor understanding
Communication/information / Communication / Mobile phone / Telephone / Driver cannot be heard
Communication/information / Communication / Mobile phone / Telephone / Driver can be poorly/hardly heard

Control unit/fault code
Control unit

Fault code

Fault text

A26/17 - Audio or COMAND
B143A11
(Head unit) (HU55) (GLC (253)
,E (213),E (238))

Microphone 1 has a malfunction. There is a short circuit to
ground.

A26/17 - MBUX multimedia sy- B143D13
stem (Head unit) (HU6) (GLS
(167),GLC (253),E (213),GLE
(167),A (177),E (238),CLA
(118),B (247))

Microphone 2 has a malfunction. There is an open circuit.

A26/17 - MBUX multimedia sy- B143A13
stem (Head unit) (HU6) (GLS
(167),GLC (253),E (213),GLE
(167),A (177),E (238),CLA
(118),B (247))

Microphone 1 has a malfunction. There is an open circuit.

A26/17 - MBUX multimedia sy- B143A11
stem (Head unit) (HU6) (GLS
(167),GLC (253),E (213),GLE
(167),A (177),E (238),CLA
(118),B (247))

Microphone 1 has a malfunction. There is a short circuit to
ground.

A26/17 - Audio or COMAND
B143A12
(Head unit) (HU55) (GLC (253)
,E (213),E (238))

Microphone 1 has a malfunction. There is a short circuit to positive.

A26/17 - Audio or COMAND
B143A13
(Head unit) (HU55) (GLC (253)
,E (213),E (238))

Microphone 1 has a malfunction. There is an open circuit.

A26/17 - Audio or COMAND
B143D11
(Head unit) (HU55) (GLC (253)
,E (213),E (238))

Microphone 2 has a malfunction. There is a short circuit to
ground.

01-08-2020 5:09 PM
© Copyright Mercedes-Benz AG

CTENORE

Page 2/4

A26/17 - Audio or COMAND
B143D12
(Head unit) (HU55) (GLC (253)
,E (213),E (238))

Microphone 2 has a malfunction. There is a short circuit to positive.

A26/17 - Audio or COMAND
B143D13
(Head unit) (HU55) (GLC (253)
,E (213),E (238))

Microphone 2 has a malfunction. There is an open circuit.

A26/17 - MBUX multimedia sy- B143D11
stem (Head unit) (HU6) (GLS
(167),GLC (253),E (213),GLE
(167),A (177),E (238),CLA
(118),B (247))

Microphone 2 has a malfunction. There is a short circuit to
ground.

A26/17 - MBUX multimedia sy- B143A12
stem (Head unit) (HU6) (GLS
(167),GLC (253),E (213),GLE
(167),A (177),E (238),CLA
(118),B (247))

Microphone 1 has a malfunction. There is a short circuit to positive.

A26/17 - MBUX multimedia sy- B143D12
stem (Head unit) (HU6) (GLS
(167),GLC (253),E (213),GLE
(167),A (177),E (238),CLA
(118),B (247))

Microphone 2 has a malfunction. There is a short circuit to positive.

Operation numbers/damage codes
Op. no.

Operation text

Time

Damage
code

Note

8210R EM Telephone function, poor communication quality/interference noise

WIS-References
Document number

Title

Note

Allocation

PE82.85-P-2110-97DBA

Wiring diagram for head unit

Cause

PE82.85-P-2110-97IBA

Wiring diagram for head unit

Cause

Attachments
MBUX VCS directionality
cue.jpg:

01-08-2020 5:09 PM
© Copyright Mercedes-Benz AG

CTENORE

Page 3/4

01-08-2020 5:09 PM
© Copyright Mercedes-Benz AG

CTENORE

Page 4/4