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

Function overview 

The instrument cluster (A1) is networked 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 (A1) does not act as an interface (gateway) between the two data bus systems. This function is reserved for the central gateway control unit (N93). This document lists the principal CAN messages for the functions of the instrument cluster (A1) including the trip computer and ASSYST PLUS system.

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

The input signals are supplied by the following components:

• The wheel speeds from the ESP control unit (N47-5) via the CAN engine compartment
• 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, selector lever position and transmission mode from the electronic selector lever module control unit (N15/5) or automated manual transmission control unit (N15/6) via the engine compartment CAN
• The fuel level in the fuel tank from the rear SAM control unit with fuse and relay module (N10/2) via the interior CAN
• The coolant temperature from the ME-SFI [ME] control unit (N3/10) or CDI control unit (N3/9) via the engine compartment CAN
• The fuel-consumption signal from the ME-SFI [ME] control unit (N3/10) or CDI control unit (N3/9) via the engine compartment CAN
• The oil level and oil temperature from the ME-SFI [ME] control unit (N3/10) or CDI control unit (N3/9) via the engine compartment CAN
• The outside temperature signal from the driver-side SAM control unit with fuse and relay module (N10/1) via the interior CAN
• The standing lamps ON/OFF signal from the driver-side SAM control unit with fuse and relay module (N10/1) via the interior CAN
• The coolant level from the driver-side SAM control unit with fuse and relay module (N10/1) via the interior CAN
• The washer fluid level from the driver-side SAM control unit with fuse and relay module (N10/1) 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 control unit (A40/3); on vehicles fitted with COMAND
• The "circuit 15R ON" and "circuit 15c" status from 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) on the multifunction steering wheel.

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 the driver-side SAM control unit with fuse and relay module (N10/1) via the interior CAN, for turn signals from the steering column module (N80) via the interior CAN, for hazard warning flashers from lower control panel control unit (N72) via the interior CAN, for ATA flashing from driver-side SAM control unit with fuse and relay module (N10/1) via the interior CAN
• Signal for brake fluid and parking brake warning lamp (A1e7) from the driver-side SAM control unit with fuse and relay module (N10/1) via the interior CAN
• Signal for ESP and ABS warning lamp (A1e41) from ESP control unit (N47-5) via engine compartment CAN
• Signal for tire pressure monitor warning lamp (A1e66) from the TPM [RDK] control unit (N88) via the CAN interior
• 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 CAN interior
• Signal for 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 engine compartment CAN
• Signal for DTR warning lamp (A1e59) from DTR control unit (N63/1) via engine compartment CAN

The airbag indicator and warning lamp (A1e15) is not actuated via the CAN bus but via a discreet line

Reception messages for the multifunction display (A1p13) 

All the signals for the messages in the multifunction display (A1p13) are received over 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 are sent by the instrument cluster (A1):

• 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
• "Terminal 58d" to the CAN engine compartment and CAN interior
• "Terminal 61e" to the CAN engine compartment
• 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 (S110) and the right multifunction steering wheel button group (S111) are voltage-coded and are read in by the steering column module (N80).
• The steering column module (N80) passes the relevant messages on the interior CAN.
• These CAN messages are received by the instrument cluster (A1). On vehicles with model designation 211.067 and 211.267, the messages from the steering wheel gear shifter MINUS (S110/1) and steering wheel gear shifter PLUS (S111/1) switches are received by the electronic selector lever module control unit (N15/5). The electronic selector lever module control unit (N15/5) processes these messages and sends CAN messages with the gear and transmission mode information to the instrument cluster (A1).
• The instrument cluster (A1) interprets these messages in combination with the systems displayed at that moment in the multifunction display (A1p13) and puts these interpreted messages as a message back on the interior CAN.

This interpretation is necessary as the function of certain pushbuttons depends on the current contents of the multifunction display

Example:

If the driver presses the + and -, specific function setting and volume control button (S111s1) of the multifunction steering wheel, this usually increases the volume. However, if the multifunction display (A1p13) is currently displaying another setting such as the interior light courtesy delay, this setting is changed when the driver presses the "+" pushbutton. The volume stays the same.

Connections 

Linking the instrument cluster (A1) to the engine compartment CAN and the interior CAN has reduced the number of inputs and outputs.

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)
• "Terminal 30" (battery positive, supplies voltage to almost all the electronics of the instrument cluster (A1)).
• "Terminal 15g" (switched positive, serves the airbag indicator and warning lamp (A1e15) and diagnostic interface of the instrument cluster (A1) as a voltage supply)
• Clock GND, ground to external clock module.
• "Terminal 15g" control input for limp-home
• Clock supply, output and battery.
• Data line for external clock.
• Input for airbag indicator and warning lamp (A1e15); this input is directly connected to the corresponding output of the restraint systems control unit (N2/7)