Comfort displays, function - GF54.30-P-3043CE

MODEL 204.0/2 as of model year 2009 

/YoM 08 

MODEL 204.3 

MODEL 204.9 

Function requirements, general 

• Instrument cluster (A1) activated

Comfort displays in general 

The comfort displays function provides a fast overview of supplemental information, which however is not required for operation of the vehicle.

The comfort display function is made up of the following subfunctions:

• Function sequence for displaying outside temperature 
• Function sequence for displaying the time 
• Function sequence for illumination of instrument cluster 
• Function sequence for output of a gearshift recommendation 

(for model 204.044/006) 

Function sequence for displaying outside temperature 

The outside temperature value is defined through the resistance value of the outside temperature display (B14). The front SAM control unit with fuse and relay module (N10/1) imports it directly, calculates the outside temperature and then sends a corresponding signal via the interior CAN (CAN B) to the instrument cluster. The outside temperature is displayed according to the country coding in either °C or °F.

In order to determine the correct outside temperature value, the following parameters must also be taken into account:

• Vehicle speed

  (falsification of value through airstream)

• Coolant temperature

(falsification of value through radiant heat)

he Electronic Stability Program control unit (N30/4) reads in the signals of the left front axle RPM sensor (L6/1), right front axle RPM sensor (L6/2), left rear axle RPM sensor (L6/3) and the right rear axle RPM sensor (L6/4) directly and sends them over the chassis CAN (CAN E) to the instrument cluster. The instrument cluster receives the signals from the RPM sensors and calculates the current vehicle speed.

The coolant temperature is recorded by the coolant temperature sensor (B11/4). The CDI control unit (N3/9) (for diesel engine) or the ME-SFI [ME] control unit (N3/10) (for gasoline engine) reads in the coolant temperature sensor signal, calculates the coolant temperature based on this and forwards the corresponding value via the chassis 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 displayed.

• Coolant temperature T > 60°C and circuit 61 ON or "PT_Rdy" (drivetrain ready) signal set:

  With vehicle speeds of v < 20 km/h (12 mph) (with vehicle deceleration) the outside temperature display is only changed when the measured outside temperature 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.

  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 circuit 61 OFF or "PT_Rdy" (drivetrain ready) signal not set:

A delay period of maximum t = 1 h prevents any apparent increase in outside temperature being displayed as a result of engine waste heat. 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 -40°C and +85°C or between -40 °F and +185 °F

The circuit 15 status is sent by the electronic ignition lock control unit (N73) over the chassis CAN and interior CAN.

If the instrument cluster receives implausible or no values at all from the outside temperature sensor, then the outside temperature display is actuated as if the coolant temperature was T > 60°C.

The outside temperature is shown on the following displays on the instrument cluster:

• Outside temperature indicator (A1p4) (model 204.0/2/3/9 (except 204.077/277/375) without code (442) Comfort multifunction steering wheel)
• Multifunction display (A1p13) (with code (442) Comfort multifunction steering wheel, model 204.077/277/375)

Function sequence for displaying the time 

The time is shown digitally on the following displays on the instrument cluster:

• Digital clock (A1p6) (model 204.0/2/3/9 (except 204.077/277) without code (442) Comfort multifunction steering wheel)
• Multifunction display (with code (442) Comfort multifunction steering wheel, model 204.077/277)

For vehicles with radio (A2) (with code (510) Audio 20 with CD changer or code (523) MB Audio 20 radio) or with COMAND control unit (A40/3) (with code (528) COMAND incl. DVD changer) the time can only be set manually using the left multifunction steering wheel button group (S110) and the right multifunction steering wheel button group (S111). The signals of the multifunction steering wheel button groups are read in by the steering wheel electronics (N135) and transmitted via the steering LIN (LIN E1) to the steering column tube module control unit (N80). The steering column tube module control unit routes the signals over the chassis CAN to the instrument cluster.

For vehicles with radio with autopilot system (A2/56) (with code (511) Audio 50 APS incl. DVD changer or code (525) MB Audio 50 APS radio) or COMAND controller unit (with code (512) COMAND APS with DVD changer or code (527) COMAND APS with single DVD drive (with navigation)), the time is synchronized with the installed audio components by the received Global Positioning System (GPS) signal.

On vehicles with code (460) Canada version, with code (494) USA version or with code (498) Japan version the time can also be set using the multifunction steering wheel button groups.

Instrument cluster illumination function sequence 

The illumination is switched on automatically when the instrument cluster is activated.

If the instrument cluster is activated via the opening of the driver's door, the illumination switches off again after t = 30 s.

If an active warning is displayed then the run-on time extends by a further t = 2 minutes.

The brightness is automatically adapted to the interior's light conditions by the brightness sensor (A1b1). Depending on the incidence of light onto the brightness sensor, the instrument cluster automatically regulates the illumination in a range between 80 and 100 % of maximum brightness.

The brightness can also be changed individually by turning the instrument illumination brightness control (A1r1) when the exterior lights are switched on.

If the light sensor (B38/1) (without code (345) Rain sensor) or the rain/light sensor (B38/2) (with code (345) Rain sensor) detects "darkness", the instrument cluster automatically switches to "Night" mode. The brightness is then approx. 50 % of the "Day" mode and it can also be adjusted using the instrument illumination brightness control.

Additional function requirements for output of a gearshift recommendation 

• Vehicle speed v > 0 km/h

(calculated by instrument cluster)

Function sequence for output of a gearshift recommendation (for model 204.044/006) 

A gearshift recommendation is shown when the engine speed and engine load reach a specified level. The display consists of an arrow indicating a recommended upshift or downshift plus the number of the recommended gear (e.g. "↑3").

The gear recommendation output is shown on the following displays on the instrument cluster:

• Display of travel distance (A1p7) (model 204.0/2/3/9 (except 204.077/277/375) without code (442) Comfort multifunction steering wheel)
• Multifunction display (with code (442) Comfort multifunction steering wheel, model 204.077/277/375)

To this end, the CDI control unit or the ME-SFI [ME] control unit evaluates the load and speed information and compares it against the current vehicle speed. The vehicle speed signal is sent to the ME-SFI [ME] control unit or CDI control unit from the instrument cluster over the chassis CAN.

The request to display the gearshift recommendation is sent from the ME-SFI [ME] control unit or CDI control unit over the chassis CAN to the instrument cluster.

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