GF54.30-P-0002RT Instrument Cluster (IC), Function

GF54.30-P-0002RT Instrument Cluster (IC), Function

Instrument cluster (A1), function
The instrument cluster serves the visual display of all dynamic and static vehicle conditions and driver information on all systems fitted in the vehicle:
^ Display of vehicle operating conditions, e.g. vehicle speed, fuel tank level, coolant temperature, rpm
^ for warning of critical operating states by means of warning and indicator lamps
^ As a central display of various systems, e.g. Audio, telephone
^ To function as a display for the "Active Service System" (ASSYST)
^ As display for the Distronic (DTR) code 219
^ Function as a trip computer

To display these states, the instrument cluster is equipped with the multifunction display (A1p13), various meters and gauges, various warning and indicator lamps, the warning buzzer (A1h1) for the acoustic warning signals, and the audible turn signal indicator (A1h2).
For the engine compartment CAN and/or interior CAN various signals, e.g. vehicle speed ("circuit 58d") are produced and passed on by the instrument cluster.
The necessary information is passed on from the various control units via the engine compartment CAN or the interior CAN to the instrument cluster, except the signal for the airbag indicator and warning lamp (A1e15), this is transmitted via a discrete line.

Via the instrument cluster a warning is displayed when the remaining distance or the remaining time up to the next service is not reached. Warning messages on the instrument cluster alert the driver to an imminent or overdue service date. Irrespective of this under certain operating conditions of the vehicle the user of the vehicle can have this and other information displayed by requesting it through the service menu on the instrument cluster.

The instrument cluster contains a microprocessor to process the incoming data.
The program and necessary data are stored in an electronic memory chip. Various menu items can be actuated via the multifunction steering wheel with the system selection button (S110s3) and the scroll forward/back button (S110s1).

Diagnosis takes place via STAR DIAGNOSIS.

Function overview
The instrument cluster is connected with the engine compartment CAN and the interior CAN. Data is exchanged with virtually all the control units over the two bus systems.

However, the instrument cluster does not act as an interface (gateway) between the two data bus systems. This function is reserved for the central gateway control unit (N93).
The basic CAN messages for the functions of the instrument cluster, including trip computer and ASSYST PLUS should be cited here.
The connections of the instrument cluster are described in the last section of this document.

The input signals are supplied by the following components:
^ The wheel speeds from the ESP control unit (N47-5) via the engine compartment CAN
^ The engine speed signal from the ME-SFI [ME] control unit (N3/10) or CDI control unit (N3/9) via the engine compartment CAN
^ The shift range and transmission mode from the fully integrated transmission control (VGS) control unit (Y3/8n4) via the engine compartment CAN
^ The drive position from the control unit for the intelligent servo module for DIRECT SELECT (A80) via the engine compartment CAN
^ The fuel tank level from the rear SAM control unit (N10/8) via the interior CAN
^ The coolant temperature from the ME-SFI [ME] control unit or CDI control unit via the engine compartment CAN
^ The fuel-consumption signal from the ME-SFI [ME] control unit or CDI control unit via the engine compartment CAN
^ The oil level from the ME-SFI [ME] control unit or CDI control unit via the engine compartment CAN
^ The oil temperature from the ME-SFI [ME] control unit or CDI control unit via the engine compartment CAN
^ The outside temperature signal from the front SAM control unit (N10) via the interior CAN
^ Standing lamp ON/OFF from the front SAM control unit via the interior CAN
^ The coolant level from the front SAM control unit via the interior CAN
^ The washer fluid level from the front SAM control unit via the interior CAN
^ Tire pressure from the TPM [RDK] control unit (N88) via the interior CAN
^ the time via the interior CAN from the audio gateway control unit (N93/1) and the latter via MOST from the COMAND operating, display and controller unit (A40/3); on vehicles fitted with COMAND
^ The condition "circuit 15R ON" and "circuit 15C" by the EIS [EZS] control unit (N73) via the interior CAN
^ The left multifunction steering wheel button group (S110) and right multifunction steering wheel button group (S111) of the multifunction steering wheel
^ VCS [SBS] off button (S110s4) and VCS [SBS] on button (S111s4) from the steering column module (N80) to the instrument cluster via the engine compartment CAN, and from this via the interior CAN to the COMAND operating, display and controller unit

The following input signals are required for indicator and warning
lamps:
^ Signal for left turn signal indicator lamp (A1e1) and right turn signal indicator lamp (A1e2)
^ Signal for high beam indicator lamp (A1e3) from front SAM control unit via interior CAN, with turn signaling from steering column module via interior CAN, with hazard warning flasher via Controller Area Network interior from lower control panel control unit (N72), with ATA flashing from front SAM control unit via interior CAN
^ Signal for brake fluid and parking brake warning lamp (A1e7) from front SAM control unit via interior CAN
^ Signal for ESP warning lamp (A1e41) from ESP control unit via engine compartment CAN
^ Signal for DTR warning lamp (A1e59) from ESP control unit via engine compartment CAN; with Distronic (DTR) Code 219
^ Signal for tire pressure monitor warning lamp (A1e66) from the TPM [RDK] control unit (N88) via the interior CAN
^ Seat belt warning lamp (A1e9) from the driver-side front seat adjustment control unit with memory (N32/1) and front passenger front seat adjustment control unit with memory (N32/2) via the interior CAN
^ Signal for engine diagnosis indicator lamp (A1e58) or CHECK ENGINE indicator lamp (A1e26) from ME-SFI [ME] control unit or from CDI control unit via engine compartment CAN.

The airbag indicator and warning lamp is not actuated via the CAN bus, but via a discreet line

Reception messages for the multifunction display
All signals for the messages in the multifunction display come via the engine compartment CAN or interior CAN.

Information about the signal paths and other details concerning the individual messages can be found in the function descriptions for the relevant systems.

The following transmitted messages come from the instrument cluster:
^ Displayed speed to passenger compartment CAN
^ Current time to the interior CAN
^ Temperature units (Celsius and Fahrenheit) to the interior CAN.
^ Headlamp switching manual/always-on (ON/OFF) to the interior CAN.
^ Interior light courtesy delay to the interior CAN
^ Headlamp switch-off delay to the interior CAN
^ Outside temperature signal to the engine compartment CAN
^ Time-controlled stationary heater operation on interior CAN
^ "Circuit 58d" to the engine compartment CAN and interior CAN
^ "Circuit 61e" to the engine compartment CAN
^ Engine OFF time to the engine compartment CAN.
^ Winter tires maximum speed to the engine compartment CAN.

CAN messages of pushbuttons of multifunction steering wheel
In view of the fact that the pushbuttons of the multifunction steering wheel perform several functions, the signals of these pushbuttons must be conditioned accordingly:
^ All the buttons of the left multifunction steering wheel button group and right multifunction steering wheel button group are voltage-coded and are read in by a LIN bus converter.
^ The steering column module reads the corresponding messages and conveys them on the interior CAN. They are then received by the instrument cluster.
^ The instrument cluster interprets these messages in combination with the systems just displayed in the multifunction display and passes these back again on the interior CAN.
^ The message from the left steering wheel gear shifter button (S110/2) or right steering wheel gear shifter button (S111/2) is received from the fully integrated transmission control (VGS) control unit. The fully integrated transmission control (VGS) control unit processes this message and sends it to the multifunction display via the engine compartment CAN.

This interpretation is necessary because the operation of some of the buttons depends on the current content of the multifunction display.
Example:
If the button + and -, setting of specific functions and volume control (S111s1) of the multifunction steering wheel is pressed, the volume of the audio system is normally increased. However if the multifunction display is just showing a setting, e.g. interior light OFF delay time, then this setting is changed when the button is pressed. The volume stays the same.

Connections
The number of connections from the instrument cluster reduces due to the connection to the engine compartment CAN and interior CAN.
The inputs and outputs (including voltage supply) are at the following connections:
^ CAN-C Low (engine compartment CAN)
^ CAN-C high (engine compartment CAN)
^ CAN-B Low (passenger compartment CAN)
^ CAN-B high (interior CAN)
^ "Circuit 31" (ground)
^ "Circuit 30" (battery positive, serves the voltage supply of almost the complete electronics of the instrument cluster.)
^ "Circuit 15g" (switched positive, serves the airbag indicator and warning lamp and diagnostic interface of the instrument cluster as a voltage supply.)
^ Clock GND, ground to external clock module.
^ "Circuit 15g" control input for limp-home
^ Clock supply, output and battery.
^ Data line for external clock.
^ Input for the airbag indicator and warning lamp (this input is directly connected to the appropriate output of the restraint systems control unit (N2/7)).