Head unit, component description - GF82.85-P-3140RF

Model 205 with code 520 (Audio 20 USB) except code 522 (Audio 20 radio) except code 531 (COMAND APS)

Model 253 with code 520 (Audio 20 USB) except code 522 (Audio 20 radio) except code 531 (COMAND APS)

Shown on MODEL 205.0

Fig 1: Identifying Head Unit And Audio/COMAND Display - Shown On Model 205.0

Courtesy of MERCEDES-BENZ USA

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 the Audio/COMAND display)

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) via telematics CAN (CAN A), evaluates them and transmits function-specific CAN messages to the user interface CAN (CAN HMI). When actuating the DYNAMIC SELECT switch (N72/4s11) (as of 01.06.2015), the AGILITY SELECT switch (N72/4s1) (up to 31.05.2015), the head unit also shows the transmission modes for selection 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

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, for example, via telematics CAN (A40/9). The signals from the upper control panel control unit, the left lower control panel and the right lower control panel are also forwarded to the head unit via the Audio/COMAND control panel and telematics CAN.
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 uses the user interface CAN to receive e.g. from the instrument cluster (A1) the signals from the left multifunction steering wheel button group (S110) and the right multifunction steering wheel button group (S111), and from the electronic ignition lock control unit (N73), the control signals for the displays in the upper control panel control unit.
Via the user interface CAN, the head unit sends 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.

Direct line

The head unit is equipped with the following direct connections:

Circuit 30g
Circuit 31
FM 1, AM, CL [ZV] and KEYLESS-GO antenna amplifier (A2/18) (input)
FM 2 and DAB band III antenna amplifier (A2/108) (model 205.0/1, model 253) or FM 2, DAB and TV 1 antenna amplifier (A2/131) (model 205.2, model 253) (input)
Audio muting from the telematics services communications module (N112/1) (with code 350 (E-Call Europe emergency call system) or with code 06U (Mercedes connect me basic services)) (input)
Hands-free system microphone (A67b1) (input)
Bluetooth® antenna (A2/91) (input and output)
USB electrical connectors (X115) (2 connections) in stowage compartment between front seats (input and output)
Audio output (speaker) (output)
Switch-on signal and power supply for mobile phone contact plate (X237/1) (with CODE 386 (Comfort telephony)) and cellular telephone system antenna amplifier/compensator (A28/15) (with CODE 386 (Comfort telephony)) (output)
Microphone output to telematics services communications module (with code 350 (E-Call Europe emergency call system) or with code 06U (Mercedes connect me basic services)) (output)
Audio output to engine sound control unit (N40/1) (with engine 276) (output)

Body

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) in the combination connector at the rear panel

Cockpit Management and Data System (COMAND) control unit wiring diagram

PE82.85-P-2101-97FBA