Display Operating Conditions, Function - GF54.30-P-3041RF

Model 205, 253 

Function requirements in general 

• Terminal 15 ON

The electronic ignition lock control unit (N73) transmits the status of circuit 15 via the user interface CAN (CAN HMI) to the instrument cluster (A1).

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 and transmission mode display (transmission 722, 724, 725) 
• Function sequence for "ECO" display 
• Function sequence for displaying transport mode 

Display of speed function sequence 

The vehicle speed is calculated from the wheel speed.

The Electronic Stability Program control unit (N30/4) transmits the information about the wheel speed over the suspension FlexRay (Flex E), the electronic ignition lock control unit and the user interface CAN to the instrument cluster. The instrument cluster calculates the vehicle speed, compares it with the internally stored speedometer characteristic, and then actuates the speedometer (A1p8) accordingly by way of a stepper motor.

Display of engine speed function sequence 

The CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) transmits information about engine speed via the engine CAN (CAN C), the drivetrain control unit (N127), the suspension FlexRay, the electronic ignition lock control unit and the user interface CAN to the instrument cluster. The instrument cluster receives the engine rpm and actuates the tachometer (A1p5) accordingly by means of a stepper motor.

Model 205, 253

with code 464 (Full display digital instrument cluster) The engine speed is not displayed permanently.

Display of coolant temperature function sequence 

The CDI control unit or ME-SFI control unit sends information on the coolant temperature to the instrument cluster via engine CAN, drivetrain control unit, suspension FlexRay, electronic ignition lock control unit and user interface CAN. The instrument cluster receives them and regulates the coolant temperature gauge (A1p1) (display with 12 segments) accordingly.

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

• T = 0 to 80°C: The actual coolant temperature is displayed. The display is not shown until T ≥ 40°C.
• T = 80 to 115°C: The coolant temperature display shows a constant value of T = 90°C.
• T = 115 to 120°C: The coolant temperature display shows a constant value of T = 95°C.
• T = 120 to 130°C (start of red warning range): The coolant temperature display shows the actual coolant temperature.

At coolant temperatures of T > 130°C, the instrument cluster also displays the coolant temperature warning lamp (A1e54). An appropriate warning message appears in the multifunction display (A1p13) of the instrument cluster. If the instrument cluster does not receive any 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 calculates the traveled distance from the wheel speed, taking the tire circumference into consideration.

The tire size is coded via the diagnostics tester.

The total distance is displayed in the multifunction display of the instrument cluster. The maximum displayed counter reading of the main odometer reading is 9.999.999. It then changes back to "0". However, the actual kilometer reading continues to be stored internally in the instrument cluster.

The trip distance is displayed in the multifunction display of the instrument cluster. The maximum displayed counter reading of the trip distance is 9999.9. If this value is reached, the figure returns to "0". The total distance is always stored in the nonvolatile memory of the instrument cluster. The current reading of the trip distance is likewise stored in the nonvolatile memory of the instrument cluster.

This memory guarantees the retention of the counter reading for at least five years even when the on-board electrical system battery (G1) is disconnected.

Display of fuel quantity function sequence 

The fill level of the fuel tank is recorded by the left fuel tank fuel level indicator fill level sensor (B4/1) and the right fuel tank fuel level indicator fill level sensor (B4/2).

Display characteristics of fuel level indicator:

• After switching on circuit 15, the current fill level is displayed.
• After an engine start, the display value is updated for t = 4 s every t = 0.8 s, to maintain a value at on-board electrical system voltage. After this time, or as soon as the vehicle starts off, the display is updated with a delay.
• After circuit 15 is switched off, the fuel level indicator is switched off.

The fuel system control unit (N118) reads in the signals of the fuel tank fuel level indicator fill level sensors and transmits information about the fill level of the fuel tank via the drive train CAN (CAN C1), the drivetrain control unit, the chassis FlexRay, the electronic ignition lock control unit and the user interface CAN to the instrument cluster. The instrument cluster receives the fill level of the fuel tank, evaluates it and regulates the fuel level indicator (A1p2) (display with 12 segments) accordingly. When the reserve range is reached (approx. 12.5 % of maximum tank capacity), the instrument cluster actuates the fuel reserve warning lamp (A1e4). An appropriate message appears in the multifunction display of the instrument cluster.

The reserve range is defined by comparing the measured fill level against the stored tank characteristic. 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.

By comparing the change in the fill level of the fuel tank against the calculated composite mileage, it is possible to determine when the fuel tank fill level sensors have jammed. If the fill level over a certain distance drops more quickly than technically feasible based on composite mileage, the fill level sensor for the fuel tank fill level sensor is recognized as being defective. An appropriate message appears in the multifunction display of the instrument cluster.

Function sequence for gear and transmission mode display (transmission 722, 724, 725) 

Information on the gear and transmission mode is displayed on the instrument cluster's multifunction display. Information on the gear indicator and transmission mode display is sent by the fully integrated transmission control unit (Y3/8n4) via drive train CAN, drivetrain control unit, chassis FlexRay, electronic ignition lock control unit and the user interface CAN to the instrument cluster.

Function sequence for "ECO" display 

The ECO start/stop function is automatically activated following each ignition change. It can be deactivated and re-activated using the touchpad (A105) (with code 446 (Touchpad only)) or the Audio/COMAND control panel (A40/9) (except code 446 (Touchpad only)).

The touchpad (with code 446 (Touchpad only)) or the Audio/COMAND control panel (except code 446 (Touchpad only)) sends the actuated selection to the CDI control unit or to the ME-SFi [ME] control unit via the telematics CAN (CAN A), head unit (A26/17), user interface CAN, electronic ignition lock control unit, suspension FlexRay, powertrain control unit and engine CAN. The CDI control unit or ME-SFI control unit checks all the function requirements and sends the status of the ECO start/stop function to the instrument cluster via the engine CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and user interface CAN. The operational readiness of the ECO start/stop function is indicated to the driver by the "ECO" symbol on the multifunction display of the instrument cluster.

If the CDI control unit or ME-SFI control unit on vehicles with transmission 716 establishes in driving mode by means of the current parameters, that it is possible for the engine to stop automatically, however neutral is not engaged, the gearshift recommendation N" is shown in the instrument cluster's multifunction display.

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 so-called delivery inspection and the final handover to the end customers.

In active transport mode, the message "Transport mode" and the charge condition of the on-board electrical system battery are shown in the instrument cluster's multifunction display in the form of a bar graph with 40 stages.

	Electrical function schematic for instrument cluster operation status display		PE54.30-P-2055-97FBA
	Overview of system components, instrument cluster (IC) component description		GF54.30-P-9996RF