Head Unit, Component Description - GF82.85-P-3140FHA
Model 238
Up To Model Year 2021
With Code 522 (Audio 20 radio)
Except Code 520 (Audio 20 USB)
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 and other multimedia devices)
- Telephony (with telephone book function)
- Internet
- - sound settings (e.g. "bass", "treble", "fader", "balance")
- System settings (e.g. "Brightness" and "Contrast" of the Audio/COMAND display (A40/8))
- Digital operator's manual
- Navigation, including voice control system for the navigation mode (with code 357 (Map navigation))
The user interface is shown on the Audio/COMAND display.
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.
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) via telematics CAN (CAN A), evaluates them and transmits function-specific CAN messages to the user interface CAN (CAN HMI). If the "Individual" transmission mode is selected using the DYNAMIC SELECT switch (N72/4s1), the head unit also shows additional selection options 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 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 from the touchpad (A105) (with code 448 (Touchpad)), for example, via the telematics CAN. The signals from the upper control panel control unit, the left lower control panel and the right lower control panel are also forwarded via the Audio/COMAND control panel and 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 receives the signals of the instrument cluster (S163/1) multifunction steering wheel button group and the head unit (S163/2) multifunction steering wheel button group and the control signals for the indicators in the upper control panel control unit, for example, via the user interface CAN.
- The head unit transmits navigation displays to the instrument cluster (A1) or the interpreted 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:
- Sound system amplifier control unit (N40/3) (with code 810 (Sound system))
- Tuner unit (A90/4) (with CODE 536 (SIRIUS satellite radio), with CODE 537 (Digital radio (DAB)))
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)
- GPS antenna (A2/23) (with code 355 (Preinstallation for navigation retrofit)) (input)
- Audio muting (mute function) from the HERMES control unit (N112/9) (with code 360 (HERMES UMTS) or with code 362 (HERMES LTE)) (input)
- HSVL line (High-Speed Video Link) from the reversing camera control unit (N66/2) (with code 218 (Reversing camera)) or from the parking system control unit (N62) (with code 235 (Active Parking Assist), with code P44 (Parking Package)) (input)
- Bluetooth® antenna (A2/91) (input and output)
- Multimedia connection unit (A90/5) (input and output)
- HSVL line for video data to the Audio/COMAND display (output)
- Wake-up for MOST (output)
- Audio output (speaker) (except code 810 (Sound system)), in vehicles with code B63 (Sporty engine sound) via the engine sound control unit (N40/1) (output)
- Activation signal and power supply for mobile phone contact plate (X237/1) (with code 379 (Telephone module Bluetooth® (SAP profile)) or with code 386 (Comfort telephony)) and to the mobile radio antenna amplifier/compensator (A28/15) (with code 386 (Comfort telephony)) (output)
- Microphone output to the HERMES control unit (with code 360 (HERMES UMTS) or with code 362 (HERMES LTE)) (output)
Ethernet
The head unit is connected to the diagnostic connector (X11/4) via Ethernet.
Structure
The following components are integrated in the head unit:
- Arithmetic unit
- Searchable database for audio files, including cover art and cover flow
- Bluetooth® receiver
- 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))
- 4-channel audio amplifier (except CODE 810 (Sound system))
- GPS receiver (Global navigation system) (with code 355 (Preinstallation for navigation retrofit))
- Gyro sensor (2D) (with code 355 (Preinstallation for navigation retrofit))
- Traffic data recorder (with code 355 (Preinstallation for navigation retrofit))
- Voice control system for navigation mode (with code 355 (Preinstallation for navigation retrofit))
- Head unit electrical fuse (A26/17f1) at the rear panel
| Wiring diagram of head unit | PE82.85-P-2110-97DCB |