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

Function overview 

The instrument cluster (A1) is connected with the following Controller Area Network (data bus/CAN-Bus) (CAN) systems:

• Controller Area Network-Bus Class C (engine compartment) (CAN-B)
• Controller Area Network-Bus Class B (interior) (CAN-C)

Data exchange between the instrument cluster (A1) and the control units listed in the following takes place via the two CAN systems.

However, the instrument cluster (A1) does not serve as an interface (Gateway) between the two CAN systems. This function is reserved for the EIS control unit (N73).

The CAN messages essential for the functions of the instrument cluster (A1), including trip computer (RRE) and Active Service System (ASSYST), are listed in the following.

The instrument cluster (A1) reads in the following input signals:

• Wheel speeds, from the ESP and BAS control unit (N47-5) via CAN-B
• Engine speed signal from ME-SFI [ME] control unit (N3/10) or from CDI control unit (N3/9) via CAN-B
• Shift range, selector lever position and driving program from electronic selector lever module control unit (N15/5) or from automated manual transmission control unit (N15/6) via CAN-B
• Tank fill level from rear SAM control unit with fuse and relay module (N10/2) via CAN-C
• Coolant temperature from ME-SFI [ME] control unit (N3/10) or from CDI control unit (N3/9) via CAN-C
• Consumption signal from ME-SFI [ME] control unit (N3/10) or from CDI control unit (N3/9) via CAN-C
• Oil fill level from ME-SFI [ME] control unit (N3/10) or from CDI control unit (N3/9) via CAN-C
• Oil temperature from ME-SFI [ME] control unit (N3/10) or from CDI control unit (N3/9) via CAN-C
• Outside temperature signal from front SAM control unit with fuse and relay module (N10/1) via CAN-B
• Standing lamp "ON" or "OFF" from front SAM control unit with fuse and relay module (N10/1) via CAN-B
• Coolant level from front SAM control unit with fuse and relay module (N10/1) via CAN-B
• Washer fluid level from front SAM control unit with fuse and relay module (N10/1) via CAN-B
• On vehicles with code (352) COMAND operating and display system the time from the COMAND operating, display and control unit (A40/3) via CAN-B
• Status "Circuit 15R ON" and status circuit 15C from EIS [EZS] control unit (N73) via CAN-B
• Signals from left multifunction steering wheel button group (S110) and right multifunction steering wheel button group (S111) of the multifunction steering wheel (MFL)
• On model 209.4 the signals of the soft top control and roll bar (RB) from the power soft top control unit (N52) via CAN-B
• Hazard warning flashing from the lower control panel control unit (N72) via CAN-B
• Direction indicator flashing from steering column module (N80) via CAN-B
• Anti-theft alarm system (ATA [EDW]) flashing from the front SAM control unit with fuse and relay module (N10/1) via CAN-B

The instrument cluster (A1) also reads in input signals for the following indicator and warning lamps:

• Left turn signal indicator lamp (A1e1) and right turn signal indicator lamp (A1e2)
• High beam indicator lamp (A1e3) from the front SAM control unit with fuse and relay module (N10/1) via CAN-B.
• Brake fluid and parking brake warning lamp (A1e7) from front SAM control unit with fuse and relay module (N10/1) via CANB.
• ESP warning lamp (A1e41) from ESP and BAS control unit (N47-5) via CAN-C
• Seat belt warning lamp (A1e9) from driver front seat adjustment control unit with memory and easy entry (N32/1) and from front passenger front seat adjustment control unit with memory and easy entry (N32/2)
• Engine diagnosis indicator lamp (A1e58) or CHECK ENGINE indicator lamp (A1e26) from ME-SFI [ME] control unit (N3/10) or CDI control unit (N3/9) via CAN-C
• DTR warning lamp (A1e59) from DTR control unit (N63/1) via CAN-C
• On model 209.4 roll bar ([RBURB]) warning lamp (A1e29) from the power soft top control unit (N52) via CAN-B

The airbag indicator and warning lamp (A1e15) is not actuated via CAN systems but via a discrete line

Reception messages for the multifunction display (A1p13) 

All signals for the messages in the multifunction display (A1p13) come via CAN-C or CAN-B.

The instrument cluster (A1) transmits the following CAN messages on the associated CAN:

• Displayed vehicle speed on CAN-B
• Current time on CAN-B
• Temperature unit in degrees Celsius (°C) or in degrees Fahrenheit (°F) on CAN-B
• Light switching "manual", "continuous", "ON" or "OFF" on CAN-B
• Interior light OFF delay time in steps of 0, 5, 10, 15, 20 seconds on CAN-B
• Headlamp switch-off delay in steps of 0,15, 30, 45, 60 seconds on CAN-B
• Outside temperature signal on CAN-C
• Circuit 58d on CAN-C and CAN-B
• Circuit 61e on CAN-C
• Engine off time on CAN-C
• Winter tire maximum speed on CAN-C

CAN-messages of the left multifunction steering wheel button group (S110) and the right multifunction steering wheel button group (S111) 

As the left multifunction steering wheel button group (S110) and right multifunction steering wheel button group (S111) have several functions, the signals of the left multifunction steering wheel button group (S110) or right multifunction steering wheel button group (S111) must be processed accordingly:

• All the pushbuttons of the left multifunction steering wheel pushbutton group (S110) and of the right multifunction steering wheel pushbutton group (S111) are voltage-coded and are read by the steering column module (N80).
• The steering column module (N80) places the corresponding CAN messages on CAN-B.
• These CAN messages are received by the instrument cluster (A1).
• The instrument cluster (A1) interprets these CAN messages in combination with the systems just displayed in the Multifunction display (A1p13) and passes on these interpreted 83 of 260 CAN messages as a CAN message on CAN-B.

The interpretation of the CAN messages is necessary, as the function of many keys of the Left multifunction steering wheel button group (S110) or right multifunction steering wheel button group (S111) depends on the current contents of the multifunction display (A1p13).

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 (A1p13) is currently displaying a setting, e.g. interior light OFF delay time, then this setting is changed when the button + and -, setting of specific functions and volume control (S111s1) is pressed. However, the volume of the audio system remains the same.

Connections 

Due to the connection of the instrument cluster (A1) to CAN-C and CAN-B the number of inputs and outputs including the voltage supply reduces to the following connections:

• CAN-C "LOW",CAN-C "HIGH"
• CAN-B "LOW",CAN-B "HIGH"
• Circuit. 31e (ground)
• Circuit 30 (battery positive)
• Circuit 15g (switched positive); serves the airbag indicator and warning lamp (A1e15) and diagnostic interface of the instrument cluster (A1) as voltage supply
• Input for the airbag indicator and warning lamp (A1e15); this input is directly connected to the corresponding output of the restraint systems control unit (N2/7)
• Clock GND ground; on external clock module
• Clock; supply, output and battery
• Circuit 15g; control input for limp-home in the event of failure of CAN-C or CAN-B
• Local interconnect network (LIN) bus data line external clock