Head Unit, Component Description - GF82.85-P-3140FH
Model 238
Up To Model Year 2021
With Code 520 (Audio 20 USB)
Except Code 522 (Audio 20 radio)
Except Code 531 (COMAND APS)
Shown On Model 238.3
Location
The head unit is centrally located in the instrument panel behind the panel at the level of the upper control panel control unit (N72/1).
Tasks
- Central operating and display unit for the entertainment and communications systems integrated in the vehicle
- 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 system (e.g. "Radio")
- Telephony (with telephone book function)
- Internet
- - sound settings (e.g. "bass", "treble", "fader", "balance")
- System settings (e.g. brightness and contrast of Audio/COMAND display (A40/8))
- Digital operator's manual
The user interface is shown on the Audio/COMAND display.
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
- Direct line
- Ethernet
CAN
The head unit is a telematics CAN and user interface CAN subscriber:
- The head unit receives the control signals from the Audio/COMAND control panel (A40/9) or the touchpad (A105) (with code 448 (Touchpad)) over the telematics CAN. The signals from the upper control panel control unit, from the left lower control panel and the right lower control panel are also forwarded by the Audio/COMAND control panel over the telematics CAN to the head unit.
- The head unit uses the telematics CAN to send e.g. control signals to the Audio/COMAND display or control signals for the displays in the upper control panel control unit to the Audio/COMAND control panel.
- 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 uses the user interface CAN to send, e.g. the interpreted signals from the left lower control panel, the right lower control panel and the signals not evaluated from the upper control panel control unit to the electronic ignition lock control unit (N73).
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) (input)
- FM 2, DAB and TV antenna amplifier (A2/108) (input)
- Left hands-free system microphone (B25/20) and right hands-free system microphone (B25/21) (input)
- Audio muting (mute function) from HERMES control unit (N112/9) (with code 360 (HERMES UMTS) or with code 362 (HERMES LTE)) (input)
- HSVL line (High-Speed-Video-Link) from reversing camera control unit (N66/2) (with code 218 (Reversing camera)) (input)
- Bluetooth® antenna (A2/91) (input and output)
- Multimedia connection unit (A90/5) for USB (Universal Serial Bus), in stowage compartment between front seats (input and output)
- HSVL line for video data to Audio/COMAND display (output)
- Audio output (speaker), in vehicles with code B63 (Sporty engine sound) over engine sound control unit (N40/1) (output)
- Switch-on signal and power supply for mobile phone contact plate (X237/1) (with code 379 (Telephone module with Bluetooth® (SAP)) or with code 386 (Comfort telephony)) or for the cellular telephone system antenna amplifier/compensator (A28/15) (with code 386 (Comfort telephony)) (output)
- Microphone output to HERMES control unit (with code 360 (HERMES UMTS) or with 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:
- Central computer
- Searchable database for audio files, including cover art and cover flow
- 3 radio tuners for AM reception, FM phase diversity and separate FM tuner function for data services, e.g. traffic messages
- 4-channel audio amplifier
- Head unit electrical fuse (A26/17f1) at the rear panel
| Wiring diagram of head unit | PE82.85-P-2110-97DCB |