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Emergency Call System, Function - GF82.95-P-0004RFB

Model 205, 253 

as of model year 2017 

with code 351 (eCall emergency call system) 

G12824511Courtesy of MERCEDES-BENZ USA

Shown on model 205 as of model year 2019, model 253.99, model 253 (except 253.99) as of model year 2020 

G12824512Courtesy of MERCEDES-BENZ USA

Shown for model 205 up to model year 2019, model 253 (except 253.99) up to model year 2020 

IMPORTANT With code 446 (Touchpad only), with code 448 (Touchpad):

Information on touchpad 

The touchpad is installed in two variants.

Variant (with code 448 (Touchpad)): The touchpad is installed together with the Audio/COMAND control panel. The touchpad is connected only to the telematics CAN.

Variant 2 (with code 446 (Touchpad only)): The touchpad is installed instead of the Audio/COMAND control panel. In this case, the left lower control panel and the right lower control panel are connected over the LCP LIN to the touchpad. The touchpad is also connected to the telematics CAN.

Function requirements, general 

Emergency call system, general 

The emergency call system allows a manual or automatic emergency call to be triggered. The emergency call is received by the Mercedes-Benz Service Center. The user is spoken to in the language that is selected in the system settings of the head unit. If necessary, the Mercedes-Benz Service Center notifies the local rescue services. If the Mercedes-Benz Service Center is not staffed, the emergency call is automatically forwarded to the local rescue services.

If the HERMES control unit receives the message "Circuit 15" from the electronic ignition lock control unit over the diagnostic CAN, it checks the operational readiness of the emergency call system. After a successful check, the emergency call system is operational and "SOS ready" appears on the Audio/COMAND display. The following checks are carried out:

IMPORTANT In the event of a fault, depending on the fault type, a fault message appears on the Audio/COMAND display and the fault code is stored in the fault memory of the HERMES control unit. If, after switching off the ignition, the Supplemental Restraint System control unit switches to the "Sleep" mode, it no longer sends a readiness signal and the "SOS NOT READY" message is shown.

The electronic ignition lock control unit transmits circuit status "circuit 15" to the HERMES control unit via the diagnostic CAN.

The emergency call system function includes the following subfunctions:

Emergency call system status indication 

The status of the emergency call system is shown in the following ways:

Status indication on the Audio/COMAND display 

The status of the emergency call system is indicated by a text message on the Audio/COMAND display in the following cases:

If an emergency call is active, the top right of the Audio/COMAND display also shows a telephone symbol, an emergency call symbol and the field strength of the HERMES control unit.

The HERMES control unit transmits the display information to the head unit via the diagnostic CAN, electronic ignition lock control unit and user interface CAN.

The head unit sends a switch-on request to the Audio/COMAND display over the telematics CAN, prepares the display and sends the image data to the Audio/COMAND display over the LVDS line (model 205 up to model year 2019, model 253 (except 253.99) up to model year 2020) or the HSVL line (model 205 as of model year 2019, model 253.99, model 253 (except 253.99) as of model year 2020) to the Audio/COMAND display.

Some text messages on the Audio/COMAND display can be confirmed using the Audio/COMAND control panel (except code 446 (Touchpad only)) or touchpad (with code 446 (Touchpad only) or with code 448 (Touchpad)). The Audio/COMAND control panel or the touchpad transmits the signals to the HERMES control unit via the telematics CAN, head unit, user interface CAN, electronic ignition lock control unit and diagnostics CAN.

Status indication via light-emitting diode 

The LED of the SOS button is used to indicate the following states:

Model 205 up to model year 2019, model 253 (except for 253.99) up to model year 2020 

The HERMES control unit transmits the request to switch on the LED to the overhead control panel control unit via the diagnostics CAN, electronic ignition lock control unit and interior CAN, front SAM control unit and roof-LIN. The overhead control panel control unit controls the LED in the SOS button.

Model 205 as of model year 2019, model 253.99, model 253 (except 253.99) as of model year 2020 

The HERMES control unit transmits the request to switch on the LED to the overhead control panel control unit via the diagnostic CAN, electronic ignition lock control unit and interior CAN. The overhead control panel control unit actuates the LED in the SOS button directly.

IMPORTANT Model 205.4

as of model year 2017

with code 351 (eCall emergency call system)

The SOS button is integrated in the emergency call system button group.

Status indication in instrument cluster 

If the HERMES control unit fails, the message "SOS nonfunctional" is displayed in the instrument cluster. The HERMES control unit continuously transmits the system status to the instrument cluster via the diagnostic CAN, electronic ignition lock control unit and user interface CAN.

Position finding 

The global navigation system GPS is used for position finding. GPS is available worldwide. GPS position finding is irretrievable after vehicle transport (e.g. by train or ferry or after towing). Recalculation of the GPS position (following an interruption in satellite reception) can take several minutes. A basic position finding routine is constantly performed in parallel to the GPS position finding routine that makes it possible to also determine the location of the vehicle if GPS reception fails.

The position finding function consists of the following component functions:

GPS position finding 

In GPS position finding, the following cases must be differentiated:

Additional function requirement for basic position finding 

Basic position finding 

The HERMES control unit requires the following signals for basic position finding:

The Electronic Stability Program control unit transmits the wheel speed and yaw rate signals to the HERMES control unit via the chassis FlexRay, electronic ignition lock control unit and diagnostic CAN.

The steering column tube module control unit transmits the signals from the steering wheel angle sensor to the HERMES control unit via the chassis FlexRay, electronic ignition lock control unit and diagnostic CAN.

The HERMES control unit uses the data to calculate the instantaneous position of the vehicle (longitude, latitude and direction of travel).

IMPORTANT Position finding errors, rolling backwards with "circuit 15 OFF" (ignition switched off) or transport of the vehicle falsify the basic position finding. In both cases, this deviation is automatically corrected on receipt of GPS data.

Manual or automatic emergency call 

In an emergency situation, a service receptionist from the Mercedes-Benz Service Center can obtain an overview of the condition inside the vehicle with the aid of the data received from the HERMES control unit (voice connection and data telegram) and initiate appropriate help measures. An emergency call be initiated manually or automatically.

These emergency calls are made for the following reasons:

IMPORTANT The automatic emergency call has priority over a manually triggered emergency call. If an automatic emergency call is triggered during a manual emergency call, the manual emergency call is interrupted. If a manual emergency call is triggered during an automatic emergency call, it is ignored. However, a data telegram containing updated position data is sent to the Mercedes-Benz Service Center, and the existing connection is maintained.

The manual or automatic emergency call function consists of the following subfunctions:

Additional function requirements for triggering an automatic emergency call 

Triggering of an automatic emergency call 

In the event of an accident with deployment of the restraint systems (not the PRE-SAFE® system) an automatic emergency call (E-call) is immediately sent. An emergency call is sent out regardless of the severity of the accident.

The HERMES control unit receives the crash information via the seat occupancy LIN as a digital crash signal from the supplemental restraint system control unit.

In addition (and redundantly), the Supplemental Restraint System control unit transmits the crash information - including the crash level - to the HERMES control unit via the user interface CAN, electronic ignition lock control unit and diagnostic CAN.

IMPORTANT The supplemental restraint system control unit cyclically sends a readiness signal via the same route as the crash information. This enables the HERMES control unit to monitor communication with the supplemental restraint system control unit and correct operation of the crash detection.

Additional function requirements for triggering a manual emergency call 

Triggering of a manual emergency call 

The manual emergency call is triggered by pressing the SOS button. The SOS button is covered up with a locking flap. Pressing the protective lid unlocks the lid, and it automatically opens with the aid of a spring mechanism.

Model 205 up to model year 2019, model 253 (except for 253.99) up to model year 2020 

The overhead control panel control unit sends the status of the SOS button over the roof-LIN, front SAM control unit, interior CAN, electronic ignition lock control unit and the diagnostics CAN to the HERMES control unit.

Model 205 from model year 2019, model 253 (except for 253.99) from model year 2020, model 253.99 

The overhead control panel control unit sends the status of the SOS button over the interior CAN, electronic ignition lock control unit and the diagnostic CAN to the HERMES control unit.

Voice connection between vehicle and Service Center 

Once the emergency call has been triggered, the HERMES control unit sets up a voice connection with the Mercedes-Benz Service Center via the emergency call system antenna. On vehicles with code 362 (HERMES LTE), additionally via the telephone antenna splitter, the left telephone antenna and right telephone antenna.

IMPORTANT Model 205, 253

as of model year 2017

with code 351 (eCall emergency call system)

with code 362 (HERMES communications module LTE)

The emergency call system antenna, left telephone antenna and the right telephone antenna are used to set up the connection to obtain transmission and reception diversity.

The status of the connection setup is indicated by the following messages on the Audio/COMAND display:

IMPORTANT The attempt to establish a voice connection to the Mercedes-Benz Service Center is canceled after several failed attempts to connect and the emergency call is automatically forwarded to the local rescue services or the following message is shown on the Audio/COMAND display: "MB emergency call activation failed. Please dial 112 on the mobile phone."

IMPORTANT Model 205, 253.99

as of model year 2019

with code 351 (eCall emergency call system)

Model 253 (except 253.99)

as of model year 2020

with code 351 (eCall emergency call system)

In the case of an automatic emergency call, the Accept/End phone call button of the head unit multifunction steering wheel button group is temporarily blocked during the connection setup to prevent any unintentional ending of the call.

While the connection is being set up, audio sources are muted (mute function) and existing telephone connections are interrupted.

For vehicles except code 810 (Sound system) and for model 205 except code 583 ("Midline" sound system), the HERMES control unit transmits the signal for the mute function directly to the head unit.

On vehicles with code 810 (Sound system), the HERMES control unit sends the signal for the mute function directly to the sound system amplifier control unit.

For model 205 with code 583 ("Midline" sound system), the HERMES control unit transmits the signal for the mute function directly to the Midline sound system amplifier control unit.

As soon as a connection is set up to the Mercedes-Benz Service Center, the HERMES control unit automatically sends a data telegram to the Service Center. The data telegram transmits the following data:

After a data telegram has been transmitted to the Mercedes-Benz Service Center, the user can speak to a service receptionist via the voice connection. The Mercedes-Benz Service Center carries out the call in the language that was selected in the system settings of the head unit and transmitted in the data telegram, where possible. For voice input, the following components are used:

The HERMES control unit receives the outgoing voice signals from the hands-free system microphone or from the driver hands-free system microphone via the head unit. The hands-free system is not available for telephone calls throughout the duration of the emergency call.

The HERMES control unit outputs the incoming voice signals over the center instrument panel speaker.

The volume of the voice output can be adjusted using the following controls:

IMPORTANT With a manual or an automatic emergency call, the Service Center can transfer the map data to the vehicle if required. The data is made available to the navigation module of the head unit.

  Electrical function diagram for manual or automatic emergency call function Model 205 as of model year 2017 up to model year 2019 with code 351 (eCall emergency call system) Model 253 (except 253.99) as of model year 2017 up to model year 2020 with code 351 (eCall emergency call system) PE82.95-P-2066-97FBD
    Model 205 as of model year 2019 with code 351 (eCall emergency call system) Model 253.99 as of model year 2019 with code 351 (eCall emergency call system) PE82.95-P-2066-97FBE
    Model 253 (except 253.99) as of model year 2020 with code 351 (eCall emergency call system) PE82.95-P-2066-97FBF
  Overview of system components, telematics Model 205, 253.99
as of model year 2017
with code 351 (eCall emergency call system)
Model 253 (except 253.99)
as of model year 2017 up to model year 2020
with code 351 (eCall emergency call system)		 GF82.85-P-9999RF 
    Model 253 (except 253.99)
as of model year 2020
with code 351 (eCall emergency call system)		 GF82.85-P-9999RFM 
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