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Home >> Mercedes Benz >> 2021 >> GT 53 AMG >> Repair and Diagnosis >> Electrical >> Motors, Switches, Relays >> Electrical System, Equipment & Instruments (2 Of 4) -- 290 Chassis >> Basic Knowledge >> Comfort Displays, Function - GF54.30-P-3043FR

Comfort Displays, Function - GF54.30-P-3043FR

Model 257, 290 

up to model year 2021 

Function requirements in general 

Comfort displays in general 

The comfort displays provide a quick overview of the information that is mot important for vehicle operation.

The comfort display function includes the following subfunctions:

Function sequence for displaying outside temperature 

The outside temperature is detected by the outside temperature sensor (B14).

The front SAM control unit (N10/6) reads in the signals of outside temperature sensor directly, calculates the outside temperature and sends this to the instrument cluster via interior CAN (CAN B), electronic ignition lock control unit (N73) and user interface CAN (CAN HMI). The outside temperature is displayed in the instrument cluster in °C  or °F, depending on the country coding.

The following parameters must also be taken into account to determine a correct value of outside temperature:

The vehicle speed is calculated on the basis of the wheel speeds.

The Electronic Stability Program control unit (N30/4) uses the wheel speeds to calculate the vehicle speed and sends the vehicle speed via the chassis FlexRay (Flex E), electronic ignition lock control unit and user interface CAN to the instrument cluster.

The CDI control unit (N3/9) (diesel engine) or the ME-SFI control unit (N3/10) (gasoline engine) sends information about the coolant temperature via the engine CAN (CAN C), the powertrain control unit (N127), the chassis FlexRay, the electronic ignition lock control unit and the user interface CAN to the instrument cluster.

The coolant temperature values have an influence on the outside temperature indicator as follows:

Coolant temperature T  < 60 °C  :

The current outside temperature value is always shown.

Coolant temperature T  > 60 °C and "Engine running" or "Drivetrain operational" signal is set: 

At vehicle speeds of v < 20 km/h (with vehicle deceleration), the outside temperature display is only changed if the measured outside temperature value drops. At vehicle speeds of v = 20 to 45 km/h, rising outside temperatures are displayed after a delay period of t = 3 min.

At vehicle speeds of v > 45 km/h, rising outside temperatures are displayed after a delay period of t = 90 s.

The CDI control unit or the ME-SFI control unit sends the "engine running" or "drivetrain operational" signal via the drivetrain CAN (CAN C1), powertrain control unit, chassis FlexRay, electronic ignition lock control unit and user interface CAN to the instrument cluster.

IMPORTANT If the vehicle speed signal is faulty, rising outside temperatures are shown every t = 10 min in an attenuated manner.

Coolant temperature T  > 60 °C  and "Engine running" or "Drivetrain operational" signal is not set: 

A delay period of maximum t = 1 h prevents any apparent increase in outside temperature caused by heat dissipated from the engine from being displayed. A rise in display value is not permitted during this delay period.

With circuit 15 OFF, the last measured outside temperature value is stored and then displayed when the circuit is reactivated.

If, in the meantime, the measured outside temperature has dropped below the stored value, the currently measured temperature is displayed after t = 8 seconds. The display range for the outside temperature is between T = -40 and +85 °C  or between T = -40 and +185°F.

The electronic ignition lock control unit sends the circuit 15 status to the instrument cluster via user interface CAN.

Function sequence for displaying the time 

The time is shown on the analog clock (A70/1) in the center console.

The time can be entered either manually in the system settings or, on vehicles with code 357 (Map navigation) or code 531 (COMAND APS), it is updated automatically by means of the received GPS data.

The head unit (A26/17) sends information on the time via the user interface CAN to the instrument cluster and onward over the user interface CAN, electronic ignition lock control unit and interior CAN to the front SAM control unit. The front SAM control unit actuates the analog clock via the instrument panel LIN (LIN 1).

Additional function requirements for instrument cluster brightness control 

Function sequence for instrument cluster brightness control 

The brightness is automatically adapted to the brightness conditions (day/night) when the instrument cluster is activated. The front SAM control unit sends information on the brightness of the instrument illumination via the interior CAN, electronic ignition lock control unit and user interface CAN to the instrument cluster.

In addition, the brightness of the displays in the instrument cluster can be also be adjusted using the settings in the "Display" menu.

IMPORTANT Detailed information on display adjustment options in the instrument cluster is available in a separate document.

Function sequence for displaying navigation images (with code 357 (Map navigation) or code 531 (COMAND APS)) 

When the navigation function is switched on, the instrument cluster displays navigation pictures.

The head unit sends corresponding video data over a high-speed video link line (HSVL) to the instrument cluster.

  Electrical function schematic of instrument cluster, comfort display   PE54.30-P-2056-97XBA
  Overview of system components, instrument cluster (IC) component description   GF54.30-P-9996FR 
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