Instrument cluster (IC), networking of components - GF54.30-P-0002-06R

The instrument cluster (A1) is linked to the engine compartment CAN and the interior CAN. Data is exchanged with both data bus systems and with practically all the control units of the two data bus systems.

The instrument cluster (A1) does not, however, act as an interface (gateway) between the two data bus systems. This function is reserved for the EIS [EZS] control unit (N73).

Below is a list of the CAN messages that are important for the functions of the instrument cluster (A1) including trip computer and ASSYST.

The connections of the instrument cluster (A1) are described in the last part of this document.

Received messages for display instruments and internal processing:

The four wheel speeds ; from the SBC control unit (A7/3n1) via engine compartment CAN
Engine speed signal ; from ME-SFI [ME] control unit (N3/10) via engine compartment CAN
The shift range, the selector lever position and the transmission mode ; from the electronic selector lever module control unit (N15/5) or from the automated manual transmission control unit (N15/6) via engine compartment CAN
Fuel tank level; from rear SAM control unit (N10/8) via interior CAN
Coolant temperature ; from ME-SFI [ME] control unit (N3/10) via engine compartment CAN
Fuel-consumption signal ; from ME-SFI [ME] control unit (N3/10) via engine compartment CAN
Oil fill level; from ME-SFI [ME] control unit (N3/10) via engine compartment CAN
Oil temperature ; from ME-SFI [ME] control unit (N3/10) via engine compartment CAN
Outside temperature signal ; from driver-side SAM control unit (N10/10) via interior CAN
Standing lamp on/off; from driver-side SAM control unit (N10/10) via interior CAN
Coolant; driver-side SAM control unit (N10/10)
Washer fluid level; from passenger-side SAM control unit (N10/11) via interior CAN
In vehicles with COMAND: time ; from the COMAND operating, display and control unit (A40/3) via interior CAN
Status of "circuit 15" and "key in ignition" ; from EIS [EZS] control unit (N73) via interior CAN
Signals from multifunction steering wheel buttons; see separate section.

Received messages for indicator and warning lamps:

Signals for left turn signal indicator lamp (A1e1) and right turn signal indicator lamp (A1e2) ;
- Turn signals from steering column module (N80) via interior CAN
- Hazard warning flashers from the lower control panel control unit (N72) via interior CAN
- ATA flashing from driver-side SAM control unit (N10/10) via interior CAN
Signal for high beam indicator lamp (A1e3); from driver-side SAM control unit (N10/10) via interior CAN
Signal for brake fluid and parking brake warning lamp (A1e7); from driver-side SAM control unit (N10/10) via interior CAN
Signal for ESP and ABS warning lamp (A1e41); from the ESP, SPS [PML] and BAS control unit (N47-5) via the engine compartment CAN
Seat belt warning lamp (A1e9); from left front seat adjustment control unit with memory (N32/1) and right front seat adjustment control unit with memory (N32/2) via interior CAN
Signal for engine diagnosis indicator lamp (A1e58) or "CHECK ENGINE" MIL (A1e26); from ME-SFI [ME] control unit (N3/10) via engine compartment CAN
Signal for DTR warning and indicator lamp (A1e59); from DTR control unit (N63/1) via engine compartment CAN
Signal for tire pressure monitor warning lamp (A1e66), from TPM [RDK] control unit (N88) via interior CAN

The airbag indicator and warning lamp (A1e15) is actuated by a discrete line, not via the CAN bus.

Received messages for left multifunction display (A1p13) and right multifunction display (A1p15):

All signals for the messages in the left multifunction display (A1p13) and right multifunction display (A1p15) are received 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.

Messages sent by the instrument cluster (A1):

Displayed speed ; to interior CAN
Current time ; to interior CAN
Temperature unit (°C/°F) ; to interior CAN
Headlamp switching manual/always-on (ON/OFF) ; to interior CAN
Interior light courtesy delay ; to interior CAN
Headlamp switch-off delay ; to interior CAN
Outside temperature signal ; to engine compartment CAN
Circuit 58 d; to engine compartment CAN and interior CAN
Circuit 61 e; to engine compartment CAN
Engine OFF time ; to engine compartment CAN
Winter tires maximum speed ; to engine compartment CAN
Signals from multifunction steering wheel buttons; see section below.

CAN messages from buttons on the multifunction steering wheel

Since the buttons on the multifunction steering wheel each have several functions , the signals from these buttons must be processed accordingly:

All the buttons in the left multifunction steering wheel button group (S110) and the right multifunction steering wheel button group (S111) are voltage-coded and are read by the steering column module (N80).
The steering column module (N80) puts the relevant messages onto the interior CAN.
These CAN messages are received by the instrument cluster (A1).
The instrument cluster (A1) interprets these messages in combination with the systems currently displayed on the left multifunction display (A1p13) and right multifunction display (A1p15) and passes these interpreted messages again as messages on the interior 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 driver presses the + and -, specific function setting and volume control button (S111s1) on the multifunction steering wheel in the (+) direction, the volume of the sound system is usually increased.

However, if the right multifunction display (A1p15) is currently displaying another setting such as the interior light courtesy delay, this setting is changed when the driver presses the (+) button. The volume stays the same.

Connections

The linking of the instrument cluster (A1) with the engine compartment CAN and the interior CAN has reduced the number of inputs and outputs (including voltage supply) to the following connections:

CAN-C LOW (engine compartment CAN)
CAN-C HIGH (engine compartment CAN)
CAN-B LOW (interior CAN)
CAN-B HIGH (interior CAN)
Circuit 31 (ground)
Circuit 30 (battery positive, supplies voltage to almost all the electronics of the instrument cluster (A1)).
Circuit 15r (switched positive, is used for the airbag indicator and warning lamp (A1e15) and for the diagnostic interface of the instrument cluster (A1) as a voltage supply).
K-line This line is connection to the data link connector (X11/4). Data is transferred from the instrument cluster (A1) when carrying out diagnosis with the STAR diagnosis tool.
Input for the airbag indicator and warning lamp (A1e15); this input is connected directly to the corresponding output of the restraint systems control unit (N2/7).
Circuit 31 Electronic clock (A70) ground
Circuit 15g Control input for limp-home
Circuit 30 Electronic clock (A70) supply, output and battery
K-line Diagnostic line
LIN bus Electronic clock (A70) data line