Head Unit, Component Description - GF82.85-P-3140FHB

Model 238 

Up To Model Year 2021 

With Code 531 (COMAND APS) 

Shown On Model 238.3 

Location 

The head unit is located behind the instrument panel cover in the center console behind the upper control panel control unit (N72/1).

Tasks 

The head unit has the following tasks:

• Central operating and display unit for the entertainment and communications systems integrated in the vehicle 
• Integration of smartphones 
• Evaluating and forwarding control signals 
• Reading in of input signals as well as actuation of output media and system components 

Central operating and display unit for the entertainment and communications systems integrated in the vehicle 

The head unit provides the user with a structured and uniform user interface for the following system components:

• Audio (e.g. radio, Bluetooth® audio, SD card (Secure Digital), Universal Serial Bus (USB) including integrated Media Interface for connecting iPhones® or MTP devices (Media Transfer Protocol)
• Telephony
• Internet (including WLAN hotspot)
• Voice control system (VCS [SBS])
• Navigation (with data from internal hard disk) including extended functions of navigation mode
• Digital operator's manual (interactive)
• Video, including TV (with CODE 865 (TV tuner))

The user interface is shown on the Audio/COMAND display (A40/8).

Using the "Vehicle functions" menu, equipment-dependent contents and functions of additional systems (e.g. climate control, seat adjustments) can be shown and controlled on the Audio/COMAND display.

Integration of smartphones 

The head unit enables the integration of smartphones by supporting the following integration standards:

• CarPlay (Apple)
• Android Auto (Google) (with code 17U (Google Automotive Link smartphone integration))
• CarLife (Baidu) (with code 18U (Baidu CarLife smartphone integration))

In order to be able to use smartphone applications, the smartphone must be connected to the front center console USB connector (X115/5) (with code 896 (Vehicle access and drive authorization through mobile phone), code 897 (Wireless mobile phone charging) or code 899 (Multifunction telephony)) or to USB connector 2 (A90/5x2) (except code 896 (Vehicle access and drive authorization through mobile phone), except code 897 (Wireless mobile phone charging) and except code 899 (Multifunction telephone)) and the integration standard selected through the "Connect" menu. If the "Automatic connection" setting has been selected, activation cannot take place via the menu.

If a smartphone is connected and the integration standard Android Auto or CarPlay is activated, the head unit is switched to a special operating mode ("Integration mode") in which not all head unit functions can be used. The following functions of the head unit are not available if Android Auto or CarPlay is activated:

• Media player
• Navigation
• Voice control system
• Telephony (with CarPlay)

The radio (AM and FM), vehicle settings and safety-related functions such as the emergency call system (with code 360 (HERMES UMTS) or with code 362 (HERMES LTE)) can still be used.

With Android Auto, the following usage restrictions apply for the telephony: Calls can only be made through the connected smartphone. Telephony with code 379 (Telephone module with Bluetooth® (SAP)) is not possible.

If an integration standard is activated, the head unit supports the smartphone apps in the following manner:

• Volume setting for all audio signals
• Forwarding of control signals to smartphone
• Use of hands-free system by the smartphone
• Forwarding of audio output to the speaker system
• Mute function, e.g. with smartphone telephony
• Forwarding of position data to smartphone
• Forwarding of video signals generated by the smartphone to the Audio/COMAND display
• Forwarding of status information for displaying in the instrument cluster (A1)

The smartphone applications themselves are not shown in the instrument cluster.

Evaluating and forwarding control signals 

The head unit receives the control signals of the left lower control panel (N72/4) and the right lower control panel (N72/5) over the telematics CAN (CAN A), evaluates them and transmits function-specific CAN messages to the user interface CAN (CAN HMI). When the DYNAMIC SELECT switch (N72/4s1) is operated, the head unit also shows the selected transmission mode on the audio/COMAND display.

Reading in of input signals as well as actuation of output media and system components 

The head unit transmits and receives signals via the following connections:

• CAN 
• Media Oriented System Transport (MOST) 
• Direct line 
• Ethernet 

CAN 

The head unit communicates over the telematics CAN with the following component parts:

• Audio/COMAND control panel (A40/9) (except code 446 (Touchpad only)):

  Control signals, communication with upper control panel control unit, left lower control panel and right lower control panel

• Touchpad (A105) (with code 446 (Touchpad only)):

  Control signals, communication with upper control panel control unit, left lower control panel and right lower control panel

• Touchpad (with code 448 (Touchpad)):

  Control signals

• Mobile phone cradle control unit (N123/8) (with code 899 (Multifunction telephony)):

  Charging requests, status of charging process, communication for drive authorization (with code 896 (Vehicle access and drive authorization through mobile phone))

• Telephone control unit (N123/9) (with code 380 (Car telephony package)):

  Status of SIM card (Subscriber Identification Module) in telephone control unit

The head unit is a user interface CAN user:

• The head unit, e.g. receives the signals of the instrument cluster multifunction steering wheel button group (S163/1) and the head unit multifunction steering wheel button group (S163/2) as well as the control signals for the displays in the upper control panel control unit over the user interface CAN.
• The head unit transmits navigation displays to the instrument cluster or the signals from the upper control panel control unit, the left lower control panel and the right lower control panel, for example, to the electronic ignition lock control unit (N73) via the user interface CAN.

Media Oriented System Transport (MOST) 

The head unit exchanges data with the following control units via MOST:

• Midline sound system amplifier control unit (N40/2) (model 238.361/461 except code 810 (Sound system) and except code 811 (Advanced sound system))
• Sound system amplifier control unit (N40/3) (with code 810 (Sound system))
• Advanced sound system amplifier control unit (N40/7) (with CODE 811 (Advanced sound system))
• TV tuner control unit (N143) (with code 865 (TV tuner))

Direct line 

The head unit is equipped with the following direct connections:

• Circuit 30t
• Circuit 31
• FM, AM, CL, DAB and KEYLESS-GO antenna amplifier (A2/18), also for the DAB 1 DAB Band III signal (input)
• FM 2, DAB and TV antenna amplifier (A2/108), also for the DAB 2 DAB Band III signal (input)
• SDAR antenna (A2/105) (with code 536 (SIRIUS satellite radio))
• Left hands-free system microphone (B25/20) and right hands-free system microphone (B25/21) (input)
• GPS signal (Global navigation system) (Input):
  • HERMES control unit (N112/9) (as of 01.06.2019 with code 362 (HERMES LTE))
  • GPS antenna (A2/23) (up to 31.05.2019 or except code 362 (HERMES LTE))
• Audio muting (mute function) from the HERMES control unit (with code 360 (HERMES UMTS) or with code 362 (HERMES LTE)) (Input)
• HSVL (High Speed Video Link) line from parking assistance systems control unit (N62) (with code 235 (Parking Pilot with PARKTRONIC), with code P44 (Parking Package)) (input)
• Bluetooth® antenna (A2/91) (input and output)
• WLAN antenna (A2/83) (input and output)
• Multimedia connection unit (A90/5) (input and output)
• Front center console USB port (with code 896 (Vehicle access and drive authorization through mobile phone), code 897 (Wireless mobile phone charging) or code 899 (Multifunction telephony)) (input and output)
• Digital instrument cluster full display fan motor (M4/12), actuation and diagnosis (with code 464 (Digital instrument cluster full display)) (input and output)
• Dedicated Short-Range Communications control unit (A50/6) (with code 498 (Japan version)) (Input and output)
• Wake-up for MOST (output)
• HSVL line for video data to Audio/COMAND display (output)
• HSVL line for video data to instrument cluster (with code 464 (Digital instrument cluster full display)) (output)
• Telephony activation signal (output) to:
  • Mobile radio antenna amplifier/compensator (A28/15) (with code 899 (Multifunction telephony))
  • Mobile phone cradle control unit (with code 899 (Multifunction telephony))
  • Mobile phone contact plate (X237/1) (with code 379 (Telephone module with Bluetooth® (SAP profile)))
• Audio output (speaker) (except code 810 (Sound system) and except code 811 (Advanced sound system)), in vehicles with code B63 (Sporty engine sound) via the engine sound control unit (N40/1) (output)
• Microphone output to the HERMES control unit (with code 360 (HERMES UMTS) or code 362 (HERMES LTE)) (output)

Ethernet 

The head unit is connected by Ethernet to the diagnostic connector (X11/4).

Structure 

The following components are integrated in the head unit:

• Arithmetic unit
• Hard disk with searchable database for audio files, including cover art, cover flow and Gracenote Database
• Bluetooth® receiver
• WLAN receiver (Wireless Local Area Network)
• 3 radio tuners for AM reception, FM phase diversity and separate FM tuner function for data services, e.g. traffic messages
• HD radio tuner (High Definition) (with code 494 (USA version))
• SDARS tuner (Satellite Digital Audio Radio Service) (with code 494 (USA version))
• DAB dual tuner (Digital radio) (except code 498 (Japan version) and except code 494 (USA version))
• 4-channel audio amplifier
• GPS receiver (Global navigation system)
• Gyro sensor and 3D acceleration sensor
• Navigation processor and traffic data recorder
• Control unit for voice control system
• Head unit electrical fuse (A26/17f1) at the rear panel

Wiring diagram of head unit

PE82.85-P-2110-97DCA