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System functions

The control unit of the instrument cluster incorporates certain functions over and above the display and indication functions, namely:

Undervoltage detection and overvoltage detection for the instrument cluster 

If the on-board voltage drops below approximately 7.5 volts, no further read or write accesses to the data memory are permitted. The instrument cluster initiates data backup in advance of a pending reset triggered by undervoltage. Overvoltage in the onboard power supply is also detected.

If the on-board voltage is greater than 16 volts:

Heating and contrast for the liquid-crystal display 

A heater built into the display ensures good legibility even at low ambient temperatures. The heater is switched on if the temperature of the liquid-crystal display is below 10 °Celsius. The switch-on signal is transmitted (by the CAS control unit to the instrument cluster via the K-CAN) when the driver's door is opened.

The contrast of the liquid-crystal display is automatically set as a function of the temperature of the liquid-crystal display and the operating time. A counter registers the standby times and operating times logged by the instrument cluster, so that due allowance can be made for ageing. Contrast voltage is automatically adjusted depending on increasing time in operation (ageing).

On-board computer functions 

There are two ways in which on-board computer functions can be displayed:

The on-board computer functions for the instrument cluster are as follows:

The on-board computer function required can be displayed: When terminal R is ON by pressing the on-board computer button on the turn-signal/main-beam switch in a specific sequence. The last line is followed by an empty line, before the first line reappears on the screen (rolling list). When terminal R switches ON, the on-board computer function most recently selected by means of the on-board computer button reappears. If the on-board computer button is pressed and held down for longer than 2 seconds, the values of the resettable on-board computer functions are recalculated.

Check-control messages 

The Check-Control system informs the driver if important functions, information or warnings are no longer available. Check-Control messages are displayed in the form of a symbol on the LCD display (red, yellow, orange).

The instrument cluster discharges the functions of priority control for the check-control messages. The readings for time and date and outside temperature are overwritten.

If a Check-Control message is present but not displayed, this will be indicated by warning triangle in the LCD display.

Supplementary notes and instructions are available for most Check-Control messages and are displayed in the Central Information Display (CID) (short form can be found in the status bar).

In addition to the visual display, the Check Control also alerts the driver with acoustic signals. Depending on the importance of the associated message, a single or double gong with varying volume and tone will sound.

Current Check-Control messages can be called up with the Check-Control button (press and hold for longer than 2 seconds) on the turn-signal/main-beam switch. The check-control messages can then be viewed in sequence (press for less than 2 seconds). When the Check-Control button is pressed, this is registered via the K-CAN.

If 8 seconds pass without a button being pressed, either the time and ambient temperature or a current Check-Control message with priority 1 will appear.

Pre-drive check 

The pre-drive check serves as:

During the pre-drive check, the most important indicator and warning lights are activated for 4 seconds when terminal 15 is switched ON. Exception: Indicator and warning lights for airbags actuated when terminal R is switched ON.

Once a pre-drive check completes successfully, all indicator and warning lights are switched off. If faults occur during the pre-drive check, the test of the systems concerned is interrupted. The indicator and warning lights for this system remain on. The check-control system issues the appropriate message.

Outside temperature compensation 

The computation model in the instrument cluster compensates for effect that the residual heat from the engine compartment has on the outside temperature signal. An increase in temperature is then only displayed with a time lag.

Condition Based Service 

Condition Based Service (CBS), as the name suggests, is a means of ensuring that the car is serviced as and when necessary. CBS has been in use in the field of service since the launch of the E65. CBS is a landmark in the increasingly close communication and networking between vehicles and Service.

The vehicle-specific scope of service required is registered automatically. In conjunction with TeleService, an automatic Service call can be placed, notifying the home dealership that Service is due.

The instrument cluster calculates when a service interval is due. When terminal 15 is switched ON, the "Next Service" indicator appears in the LCD display (remaining visible for 6 seconds). The countdown distance or the countdown time is also shown.

More information on CBS can be called up at the same time on the central information display (CID).

The service interval can be reset by means of the reset button in the instrument cluster (press and hold down for longer than 5 seconds). The target date for the vehicle inspection and emissions test can only be entered in the CID via the controller.

Vehicle identification check 

The information stored redundantly in the instrument cluster and the CAS control unit (Car Access System) is:

The vehicle identification number and odometer are used to prevent manipulation. Information about manipulation is given by a warning light.

CBS data are important in service (KeyReader and service reception module (SAM)). These data must not be lost.

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