Display Operating Conditions, Function - GF54.30-S-3041TRF

Model 447 

With Code XM0 (Facelift) 

Except Code ME0 (Electric motor 85 kW) 

Except Code ME4 (Electric motor 145 kW) 

Function requirements in general 

• "Terminal 15 ON"

The electronic ignition lock (EZS) control unit (N73) sends the status of terminal 15 to the instrument cluster (IC) control unit (A1/1).

Display operating conditions, general 

The operating conditions display provides the driver with permanent information about the current operating conditions of the vehicle.

The "display operating conditions" function comprises the following subfunctions:

• Display of speed function sequence
• Display of engine speed function sequence
• Display of coolant temperature function sequence
• Display of travel distance function sequence
• Display of fuel quantity function sequence
• Function sequence for gear display or drive program display
• Function sequence for "ECO" display
• Function sequence for displaying transport mode
• Function sequence for displaying AdBlue® fluid fill level

Display of speed function sequence 

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

The Electronic Stability Program (ESP) control unit (N30/4) calculates the vehicle speed from the wheel speeds and sends the calculated vehicle speed to the instrument cluster (IC) control unit.

The instrument cluster (IC) control unit compares this with the internally stored speedometer characteristic and actuates the speedometer (A1/1p8) accordingly via a stepper motor.

Display of engine speed function sequence 

The CDI control unit or the ME control unit sends information on the engine speed to the instrument cluster (IC) control unit. The instrument cluster (IC) control unit receives the engine speed and actuates the tachometer (A1/1p5) accordingly via a stepper motor.

Display of coolant temperature function sequence 

The CDI control unit or the ME control unit sends information on the coolant temperature to the instrument cluster (IC) control unit. The instrument cluster (IC) control unit receives this and accordingly actuates the coolant temperature gauge.

The coolant temperature gauge is actuated via a correction characteristic. This correction characteristic defines the following 4 temperature ranges in which the coolant temperature display is actuated in different ways:

• 0 to 80°C: The actual coolant temperature is displayed. However, the display is only shown from 40°C and above.
• 80 to 115°C: The coolant temperature display constantly shows a value of 90°C.
• 115 to 120°C: The coolant temperature display constantly shows a value of 95°C.
• 120 to 130°C (start of red warning range): The coolant temperature display shows the actual coolant temperature.

At coolant temperatures of > 130°C, the instrument cluster (IC) control unit additionally actuates the coolant temperature warning lamp (A1/1e54). A corresponding warning appears in the multifunction display (A1/1p13) of the instrument cluster (IC) control unit. If the instrument cluster (IC) control unit does not receive a value for the coolant temperature, it actuates the coolant temperature warning lamp. The coolant temperature gauge is then not actuated.

Display of travel distance function sequence 

The instrument cluster (IC) control unit uses the wheel speeds to calculate the traveled distance, taking the tire circumference into consideration.

The tire size is coded via the vehicle diagnosis system.

The total distance is shown in the multifunction display of the instrument cluster (IC) control unit. The maximum displayed counter reading of the total distance is "9, 999, 999". It then changes back to "0". However, the actual kilometer reading continues to be stored internally in the instrument cluster (IC) control unit.

The trip distance is shown in the multifunction display of the instrument cluster (IC) control unit. The maximum displayed counter reading of the trip distance is "9999.9". Once this value is reached, it changes back to "0". The total distance is continually stored in the nonvolatile memory of the instrument cluster (IC) control unit. This memory ensures that the counter reading is retained for at least 5 years, even when the on-board electrical system battery (G1) is disconnected. The current trip distance is also stored in the nonvolatile memory of the instrument cluster (IC) control unit.

Display of fuel quantity function sequence 

The fill level of the fuel tank is detected by the fill level sensor integrated in the fuel pump with fuel feed module (M3/3). To do so, the fuel system control unit (FSCU) reads in the signals from the fill level sensor directly and sends information on the fill level of the fuel tank to the instrument cluster (IC) control unit.

The instrument cluster (IC) control unit receives the fill level of the fuel tank, evaluates this and actuates the fuel level indicator accordingly.

If the reserve range has been reached (approx. 12.5 % of the maximum tank capacity), the instrument cluster (IC) control unit actuates the fuel reserve warning lamp (A1/1e4). A corresponding message additionally appears in the multifunction display of the instrument cluster (IC) control unit.

The reserve range is defined by comparing the measured fill level with the tank characteristic stored in the instrument cluster (IC) control unit. If the reserve range drops to approx. 50 %, a gas station symbol in the form of a gasoline pump is shown in the "Range" menu instead of the distance reading.

Display characteristics of fuel level indicator:

• After circuit 15 is switched on, the current fill level is displayed.
• In the first 4 s after engine start, the display value is updated every 0.8 s in order to obtain a value under the full on-board electrical system voltage. After this time, or as soon as the vehicle starts off, the display is updated with a delay.
• After terminal 15 is switched off, the fuel level indicator is also switched off.

The instrument cluster (IC) control unit receives the fill level of the fuel tank, evaluates this and actuates the fuel level indicator accordingly.

Jamming of the fill level sensor is detected by comparing the change in fill level of the fuel tank with the calculated composite mileage. If the fill level over a certain distance drops more quickly than technically feasible based on the composite mileage, the fill level sensor is recognized as being defective. A corresponding message appears in the multifunction display of the instrument cluster (IC) control unit.

Function sequence for gear display or drive program display 

The gear or drive program information is shown in the gear display or drive program display in the display of the instrument cluster (IC) control unit. Information on this is sent by the CDI control unit or the ME control unit to the instrument cluster (IC) control unit.

Function sequence for "ECO" display 

Model 447.6/7: 

• The ECO start/stop function is automatically activated after every ignition change and can be deactivated and then activated again using the ECO start/stop function button (N72/1s5).
• The upper control panel (UCP) control unit (N72/1) sends the actuated selection to the CDI control unit or the ME control unit.

Model 447.8: 

• The ECO start/stop function is activated automatically following each ignition cycle and can be deactivated and activated again via the central operating unit (COU) control unit (A40).
• The central operating unit (COU) control unit sends the actuated selection to the CDI control unit or the ME control unit.

The CDI control unit or the ME control unit checks all the function requirements and sends the status of the ECO start/stop function to the instrument cluster (IC) control unit. The operational readiness of the ECO start/stop function is indicated to the driver by means of the "ECO" symbol in the multifunction display of the instrument cluster (IC) control unit.

If, while the vehicle is being driven, the CDI control unit or the ME control unit detects on the basis of the current parameters that automatic stopping of the engine is possible, but neutral has not been engaged, the gearshift recommendation "→ N" is shown in the display of the instrument cluster (IC) control unit.

Function sequence for displaying transport mode 

Transport mode is activated at the factory at the end of the production process and sets the entire vehicle to a defined special state (e.g. limited vehicle speed or restricted outside lamp functions).

The transport mode remains active on its way from the production plant to the dealers and company-owned sales and service outlets around the world up to the delivery inspection and the final handover to the end customers.

In active transport mode, the message "Transport mode" and the charge level of the on-board electrical system battery are shown in the multifunction display of the instrument cluster (IC) control unit in the form of a bar graph with 40 stages.

Function sequence for displaying AdBlue® fluid fill level 

The fill level of the AdBlue® container is read in by the AdBlue® (SCR) control unit (N141) and sent to the instrument cluster (IC) control unit.

Overview of system components of instrument cluster (IC) control unit

GF54.30-S-9989TRF