Various versions of the instrument cluster are fitted. The functions of the instrument cluster are shown in a number of display areas. In addition, acoustic warnings are issued in connection with several visual displays. The instrument cluster has diagnostic capability on diagnosis testers. Self-test functions are also integrated. On-board computer functions can be coded. The functions are displayed with:
Pointer instruments:
LC display area 1:
LC display area 2:
Indicator and warning lamps: The instrument cluster contains the following 24 indicator and warning lamps (as symbols or lettering):
Acoustic warnings/messages: Acoustic warnings/messages are issued to supplement some indicator and warning lamps (with the exception of turn indicators) via a loudspeaker as a single tone or as a continuous tone for:
Event/Warning |
Output |
Priority |
|---|---|---|
Turn signal display cycle |
synchronous for visual turn indicator lamp check |
1 |
Ignition key warning (only USA) |
intermittent |
1 |
Seat-belt warning (country versions) |
intermittent |
1 |
Speed warning (only Gulf states) |
once |
1 |
Parking brake applied |
intermittent |
2 |
Coolant high temperature |
single |
2 |
Tyre Defect Indicator (RPA) (tyre pressure loss) |
single |
2 |
Oil level (oil loss/oil consumption) |
single |
2 |
DSC failure |
single |
2 |
Limit warning, on-board computer (can be set) |
single |
2 |
Gear warning SMG |
single |
2 |
Lighting on |
intermittent |
3 |
Outside temperature ≤ 3°C |
single |
3 |
The K bus (Body Electronics) is used for data exchange between the control units of the body electronics and the instrument cluster. Data is exchanged by means of data telegrams.
The PT CAN bus (Powertrain CAN bus) is used for data exchange between the engine electronics, the Dynamic Stability Control (DSC) and the instrument cluster. Data is exchanged by means of data telegrams. In the case of automatic gearboxes, the EGS control unit is also connected.
The D bus (diagnostic bus) is used for data exchange between the instrument cluster and a testing device. Data is exchanged by means of data telegrams.
For control units that have no separate diagnosis lead but are attached to the K bus, the instrument cluster performs the gateway function for the telegram transport of the diagnosis.
The byteflight is connected to the K bus via the Safety and Information Module (SIM), which acts as a gateway. Via this bus connection, the information from the satellites SBSL and SBSR is transferred to the instrument cluster.
The control unit, circuits for signal processing, the power supply and operating and display elements are integrated in the instrument cluster.
The instrument cluster has the master function for other equipment attached to the bus and, as gateway module, connects the PT CAN bus (Powertrain bus), the K bus (Body Electronics bus), the D-bus (diagnostic bus) and the byteflight. Information is exchanged by means of data telegrams. The instrument cluster also receives signals directly from sensors.
Encoding data and nonvolatile counter levels are stored in the instrument cluster.
The two buttons S/R (Set/Reset) on the left and the clock symbol (right) can be used to make the following settings:
S/R button
Clock symbol button (right):
The axial button in the steering-column lever (LSS) for the turn indicators can be used to trigger the evaluation of the on-board computer. It can also be used to select the digital clock or outside temperature display.
The lights switching centre (LSZ) activates the lighting for the instrument cluster. The lights switching centre (LSZ) also controls the brightness of the dial face, pointer and display illumination. The information is transferred by means of data telegrams via the K bus to the instrument cluster.
As of terminal 30 (terminal R and terminal 15 OFF), the instrument cluster is on standby. The circuit parts that are not required are disabled to reduce quiescent current (sleep mode). The clock module for real time, SIA time and periodical outside temperature measurement continues to run. Interrupts are performed by the K bus and S/R button. In the case of terminal 30 operation, the K bus and displays are inactive.
For display of travel distance and time, the instrument cluster can be wakened using the S/R button. Following a period of 25 seconds, the instrument cluster returns to the Sleep mode. During the display period, no buses are wakened.
The gear display, Check Control indicator lamp and the sensors for coolant level, brake pads, etc. become active as of terminal 15 On. Communication with engine, gearbox and chassis control units is handled via the PT CAN bus. All interfaces of the instrument cluster are active.
The status of terminal 30h (terminal 50 starter motor) is registered by a digital input and made available to the system. During the start operation, the evaluation of signal inputs is restricted. If terminal 30 is on, no A/D conversions are evaluated. Digital input information, e.g. from buttons, is not used either.
The power supply of the instrument cluster is by means of a switching controller. The switching controller compensates for voltage fluctuations of the vehicle electrical system in the range from 9 V to 16 V.
Undervoltage: the vehicle voltage is measured as of terminal 30 every 30 milliseconds. As of a voltage of approx. 7,5 V, undervoltage is detected. Then, no more read and write accesses are permitted to the EEPROM. Prior to a possible undervoltage reset, the instrument cluster initiates a data backup.
Overvoltage: overvoltage is detected in the case of a voltage >16 V. The microcontroller initiates measures to back up the hardware. Data (mileage, SIA data, time, date, etc.) or states are not lost because they are stored in good time. Indicator and warning lamps are switched off or dimmed for the duration of the overvoltage.
The control units of the Dynamic Stability Control (DSC) and instrument cluster communicate across the PT CAN bus. In addition, the two control units are also connected by cables to ensure redundant information transfer.
On one cable, the travelled distance signal processed by the DSC control unit is transferred from the rear left ABS speed sensor. The signal is used to calculate the travelled distance and the travelling speed.
On another cable, the signal for activation of the ABS warning lamp is transferred. This signal is displayed in the event of malfunctions in the braking control system as well as PT CAN bus failure. If it is detected that the signal is missing on this cable, a break in the plug-in connection on the DSC control unit is also detected (legal requirement).
The redundant data storage function is described in the functional description of the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units
The Service Interval Display (SIA) function is described in the functional description of the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units
The Keyreader and SAM 1 functions are described in the functional description of the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units
The instrument cluster is the interface between the K bus, PT CAN bus and diagnostic bus. The instrument cluster communicates with other control units in the vehicle across the (single-wire) K bus and the (double-wire) PT CAN bus. Here, the instrument cluster transmits/receives messages to/from equipment attached to the bus. The connection to the diagnosis tester is via the (single-wire) diagnostic bus.
The instrument cluster performs the following gateway functions in the bus interconnection:
For control units without diagnosis interface, the instrument cluster maintains the dialogue with the diagnosis tester. For this purpose, the instrument cluster implements the K bus telegrams of these control units on the diagnostic bus.
Example (only for USA): In the case of the function of the two-stage Brake Force Display, the DSC control unit (PT CAN bus) transmits the information 'longitudinal deceleration' (braking) to the instrument cluster. If a threshold value coded in the instrument cluster is exceeded, the lights switching centre (LSZ) receives the instruction across the K bus to activate the brake lights with stage 1 or stage 2.
The information flow across the bus interconnection is as follows:
---> DSC === PT CAN === instrument cluster ---- K bus ---- LSZ --->
NOTE: The diagnosis is described in the functional description of the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units
Lighting: the instrument cluster is illuminated as of terminal R On. For switching on, the signal 'Light ON' is sent across the K bus by the lights switching centre (LSZ) to the instrument cluster. The voltage is supplied by a switching controller in the instrument cluster.
The road speed and engine speed displays are lit by split-light illumination (emitted light between dial and dial face). The LC display areas 1 (in the speedometer) and 2 (program and gear display) are composed of orange-coloured segments.
The lights switching centre (LSZ) controls the brightness of the dial face, pointer and display illumination (instrument dimmer). To control the instrument dimmer, the lights switching centre (LSZ) evaluates the signals from the dimmer (dimmer wheel) and the photocell on the lights switching centre (LSZ) to determine the surrounding brightness. The dimmer signal is transmitted across the K bus.
The travelling speed is derived from the current number of travel impulses from the ABS control unit as of terminal 15 ON. The travelling speed is displayed in analog form in the left-hand instrument dial. The needle is driven by a step motor. The scale is country-specific (country variant).
The information regarding the current engine speed is supplied to the instrument cluster as of terminal 15 ON by the engine electronics across the PT CAN bus.
The engine speed is displayed in analog form in the right-hand instrument dial. The engine speed is scaled in revolutions per minute (rpm). A red warning field signals the overspeed range. The needle is driven by a step motor.
Information corresponding to the coolant temperature is supplied to the instrument cluster as of terminal 15 ON by the engine electronics across the PT CAN bus. This information is displayed in analog form in the small, right-hand instrument dial in the revolution counter. The needle is driven by a step motor. In the case of high temperature, the maximum movement of the pointer is to the middle of the red warning zone. The warning field is simultaneously an indicator lamp. Circuitry measures prevent that the display is moved into the red warning zone following a hot start.
Independent of the dial position, an overtemperature display can be activated by the engine electronics across the PT CAN bus.
Fuel-tank sensors L and R receive their 5 V of power from the switching controller in the instrument cluster. The signals from the two fuel-tank sensors are read in separately. The tank content is calculated in the instrument cluster from the signals from the fuel-tank sensor and other set quantities. The calculated fuel rate is displayed in analog form with the small left-hand instrument dial in the revolution counter. The needle is driven by a step motor.
When a factory-coded reserve threshold (standard = 8 litres) is reached, an additional tank-reserve lamp is switched on. The lamp is prevented from flickering by software hysteresis.
The data corresponding to the available fuel is provided as telegrams on the PT CAN bus, the K bus and the diagnostic bus for control units and service.
As of terminal 15 On, the ABS control unit sends the travel signal to the control unit of the instrument cluster. The distance is derived in 10-m increments from the travel signal. The values are totalled in the memory for the total distance travelled and trip distance recorder (GWSZ and TWSZ). Each kilometre is saved by the distance recorder (GWSZ).
For cases involving replacement, there is an additional redundant backup every 100 km of the mileage in km and the SIA data in the lights switching centre (LSZ). At the same time, the kilometre reading and the SIA data are transferred via K bus to the electronic vehicle immobilisation unit (EWS). (The customer authorisation key is provided with data from the EWS (vehicle immobilisation unit).
The total mileage is converted into km or miles on a country-specific basis. The value is displayed as a six-digit number. Display in the LC display is as of terminal R On or with terminal 30 for 25 seconds after actuating the S/R button.
The trip odometer is also converted into km or miles on a country-specific basis. The value is displayed as a four-digit number. Display in the LC display is as of terminal R On to the exact tenth of a kilometre or tenth of a mile.
The odometer and trip distance recorder can be switched on independently of terminal R On. Both travel distances are always displayed simultaneously. The trip-distance counter can be reset to zero any number of times using the S/R button as of terminal R ON.
With terminal R On, the first display that appears is the Service Interval Display (SIA) for 5 seconds in display 1. During this period, operations of the axial button in the steering column lever (LSS) for turn indicators are ignored. The time is then displayed. The time can be adjusted using the S/R button and the clock symbol button on the instrument cluster as well as via the on-board computer. A clock that has not been set, e.g. after a longer power interruption of terminal 30, is indicated by dashes with a flashing colon.
As of terminal R, the time is sent on the K bus for display on the Multi Information Radio (MIR) or Central Information Display (CID).
Depending on coding, the time can be displayed in the 12-hour or 24-hour mode. It is changed over by pressing the axial button in the steering-column lever (LSS) for turn indicators for a longer period (> 5 seconds). The 12-hour setting is displayed by activating AM and PM.
Setting the clock with the S/R and clock symbol buttons:
To call up the setting mode:
To set the hours:
To set the minutes:
To restart the clock:
Setting the clock via on-board computer:
If the minute setting is changed, the seconds are set to zero.
The manipulation point is displayed to the left of the trip distance recorder in LC display area 1. It is switched on when a comparison shows that the vehicle identification numbers stored in the instrument cluster and in the lights switching centre (LSZ) (redundant data storage) do not match. One cause of this can be replacement of one of these control units.
NOTE: With regard to matching up the vehicle identification numbers (switching off the manipulation point) and replacing control units, refer to the functional description for the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units
The Check Control indicator lamp (lamp faults) is described in the functional description of the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units
The indicator and warning lamps (symbols or lettering) are lit by soldered LEDs. Some LEDs are designed in two colours.
Display / Symbol |
Colour |
Activation of |
Active as of |
|---|---|---|---|
Turn signal indicators, left and right |
green |
LSZ (K bus) |
Terminal R, hazard warning lights, terminal 30 |
Charge indicator lamp (terminal 61) |
red |
DME (PT CAN bus) |
Terminal 15 |
High beam / headlight flasher |
blue |
LSZ (K bus) |
Terminal R |
Oil pressure too low Oil level low |
red yellow |
DME (PT CAN bus) or oil-pressure switch (in the case of 4-cylinder engine) DME (PT CAN bus) |
Terminal 15 |
ABS (anti-lock braking system) inactive |
yellow |
DSC via separate cable |
Terminal 15 |
General brake warning lamp: - Parking brake - Brake-fluid level low - EBV (Electronic Braking Force Distribution) inactive DBC (Dynamic Braking Control) inactive (if coded) |
yellow / red red red red yellow |
Hand-brake switch DSC (PT CAN bus) DSC (PT CAN bus) DSC (PT CAN bus) |
Terminal 15
Terminal 15 |
Brake pad wear |
yellow |
Brake pad sensors and algorithm in instrument cluster |
Terminal 15 |
Fog lamps |
green |
LSZ (K bus) |
Terminal 15 and terminal 58 |
Rear fog light (not USA) |
yellow |
LSZ (K bus) |
Terminal 15 and terminal 56 |
EPS (Electromechanical Power-assisted Steering) |
yellow |
EPS (PT CAN bus) |
Terminal 15 |
Tyre Defect Indicator (RPA) (tyre pressure loss) / system failure or in the case of initialisation (tyre change, tyre pressure change) |
yellow
red |
DSC (PT CAN bus) |
Terminal 15 |
Airbag |
red |
ASE (K bus) |
Terminal 15 |
Seat belt warning (can be coded on country-specific basis) |
red |
ASE (K bus) |
Terminal 15 |
Check Control (lamp faults) |
yellow |
LSZ (K bus) |
Terminal 15 |
Gearbox emergency program |
yellow |
EGS/SMG (PT CAN bus) |
Terminal 15 |
EML (Electronic Throttle Control) |
yellow |
DME (PT CAN bus) |
Terminal 15 |
Engine electronics (SERVICE ENGINE SOON in USA) |
yellow |
DME (PT CAN bus) |
Terminal 15 |
ASC (Automatic Stability Control) (regulating or is inactive) |
yellow |
DSC (PT CAN bus) |
Terminal 15 |
DTC (Dynamic Traction Control) regulating |
yellow |
DSC (PT CAN bus) |
Terminal 15 |
Coolant level low |
yellow |
Coolant level switch |
Terminal 15 |
Coolant high temperature |
red |
DME (PT CAN bus) |
Terminal 15 |
Open fuel tank catch (CHECK GAS CAP, only USA) |
yellow |
DME (PT CAN bus) |
Terminal 15 |
Fuel reserve |
yellow |
Fuel-tank sensor and algorithm in instrument cluster |
Terminal 15 |
The acoustic seat-belt warning is issued for EU (USA: Seat Belt Reminder) for the driver and passenger side. It is now possible to issue the seat-belt warning by fitting belt buckles that have so far only been used in US vehicles. In addition, the seat occupation detection (SBE) detects whether the passenger seat is occupied. After a travel distance of 100 metres or during a trip, the instrument cluster issues an intermittent acoustic warning for a maximum of 90 seconds.
The seatbelt buckle information is transferred by the airbag control unit across the K bus to the instrument cluster.
The pre-drive check is described in the functional description of the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units
The on-board computer function in the instrument cluster can be coded in two versions.
In the low version for on-board computer, only the outside temperature is displayed in LC display area 1. The time is then displayed on the radio display. However, the clock setting is performed using the S/T buttons on the instrument cluster.
In the high version for on-board computer, the individual functions can be called up successively in the coded order. To do so, press the axial button in the steering-column lever (LSS) for turn indicators. The functions are displayed continuously on the LC display, display area 1, or on the Multi Information Radio (MIR) or the Central Information Display (CID).
The units of the selected on-board computer functions are shown on the LC display (l/100 km, km/l, mls/gal US or mls/gal UK) according to the coding.
In the case of vehicles without radio, there is no outside temperature display. On such vehicles, only the time is displayed in the bottom line in LC display 1.
The order of the on-board computer functions shown in LC display 1 is always the same.
There is a display combination option of time and outside temperature, depending on the equipment.
NOTE: For vehicles without radio special equipment, there is no outside temperature display in the instrument cluster. Only the time is displayed in the bottom line of LC display 1.
If the outside temperature display is flashing (temperature ≤ 3°C), each on-board computer function currently on display is hidden.
With terminal R On, the on-board computer displays the on-board computer function that was last displayed. Other displays can be called up by briefly pressing (< 2 seconds) the axial button in the steering-column lever (LSS) for turn indicators. Pressing for a longer period (> 2 seconds) enables settings to be made or a reset of the selected computer functions.
The on-board computer functions 'average fuel consumption' and 'average speed' can be reset by briefly pressing (< 2 seconds) the axial button in the steering-column lever (LSS) for turn indicators. The average calculation for both displays is then restarted.
When the limit warning (or speed warning, country versions) is reached, the road-speed value displayed in LC display 1 flashes. A warning tone is issued.
The distance to the next turnoff is provided to the instrument cluster by the navigation computer via the K bus. The remaining distance display is a staggered representation in LC display 1.
If the vehicle is moving towards a junction, the distance from 400 metre to 100 metres is displayed in 100-metre steps.
As of 100 metres, the distance is then displayed in 10-metre steps.
NOTE: At higher speeds, e.g. on motorways, the distance information is displayed 1000 m before the junction (motorway exit).
After the turn has been completed, the previously displayed on-board computer function reappears.
On vehicles with Multi Information Radio (MIR), the on-board computer functions are also shown in the radio display. On addition, the on-board computer function 'Average fuel consumption 2' is displayed. The list can be scrolled using the rotary push button. A date display is possible.
Settings made using the rotary push button, such as units or resets, are transmitted by data telegram to the instrument cluster. The values that applied until then are updated.
The date is managed in the instrument cluster and shown in the radio display.
NOTE: Following a power interruption (e.g. battery replacement), the current year stored in the instrument cluster is displayed.
On vehicles with high navigation system, the on-board computer functions are displayed in the Central Information Display (CDI). The navigation information 'Distance to junction' is shown in parallel in the instrument cluster.
Settings made using the rotary push button on the control panel of the navigation system, such as units or resets, are transmitted by data telegram to the instrument cluster. The values that applied until then are updated.
The date can be set using the ”Settings” function on the Central Information Display (CDI). However, the date is managed and displayed in the instrument cluster (no status bar in the Central Information Display (CDI)).
The outside temperature is recorded by means of a sensor (NTC resistor) in the bumper. The sensor is connected to the power supply of the instrument cluster. The analog voltage value coming from the sensor is digitised in the instrument cluster. Then, depending on the engine temperature and travelling speed, it is processed for the display.
When the outside temperature is displayed, the unit display can be changed. Pressing the axial button in the steering-column lever (LSS) for turn indicators for a longer period (> 5 seconds) switches the unit from °C to °F and vice versa.
As of terminal R On, the display can be changed using the axial button in the steering-column lever (LSS) for turn indicators. The order is: time of day, outside temperature, average fuel consumption, cruising range, average vehicle speed. Each time the axial button in the steering-column lever (LSS) for turn indicator is released, a jump is made to the next function.
If the outside temperature falls below +3°C, an acoustic outside-temperature warning is issued. The outside temperature display then flashes for a few seconds. The outside-temperature warning can be cancelled by briefly pressing (< 2 seconds) the axial button in the steering-column lever (LSS) for turn indicators. After the cancellation, the previously displayed on-board computer function reappears.
Depening on the coding, the outside temperature display remains in the display after an outside-temperature warning or the display moves back to the on-board computer function last displayed (e.g. time).
During an SIA display, no outside-temperature warning is displayed.
At temperatures below -5°C, the temperature gauge does not flash at terminal R On. Flashing only begins after running through the display options using the axial button in the steering-column lever (LSS) for turn indicators.
The next outside-temperature warning is possible after +6°C is exceeded and then falls below +3°C once again or terminal R is switched on again.
The car and key memory function are described in the functional description of the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units
LC display area 2 for the program and gear display is located below the indicator and warning lamps between the large pointer instruments. In the case of the automatic gearbox version and sequential M-transmission (SMG), the engaged gear and selected gearbox program are displayed in LC display area 2. In the event of a fault, the gearbox emergency program symbol is displayed in a separate indicator lamp. The display function can be coded. The coded function (without, automatic, SMG) is displayed as of terminal 15 On.
Program mode (left) |
|---|
M (= manual) |
S (= Sport) |
D (= automatic mode, only SMG) |
F (= fault, only SMG) |
Gear (right) |
|---|
P |
R |
N |
D |
1 to 6 |
The SMG display can also be displayed after terminal 15 R Off as long as the SMG control unit transmits information. In addition, the SMG can flash the display and issue an acoustic warning via the PT CAN bus.
In the case of automatic gearbox and SMG, the gearbox information is transmitted from the gearbox control unit across the PT CAN bus. The data received by the instrument cluster is displayed as of terminal 15 On. A fault in the gearbox or failure of the PT CAN communication triggers display of the gearbox emergency program with a separate indicator lamp. The function can be coded. If the message fails, a fault code memory entry is made in the instrument cluster.
On manual gearbox vehicles, the reverse gear signal is read in via connector pins. In order to enable output of the reversing signal across the K bus also in the case of manual gearboxes, there is a digital input for this signal on the instrument cluster. If the instrument cluster is coded for a manual gearbox, it reads the information via the input. The current status ”reverse gear engaged” is always provided across the K bus to other equipment attached to the bus such as mirror memory, Park Distance Control (PDC), etc.
NOTE In the case of SMG, selector-lever position N flashes after the vehicle has been parked. Flashing is the visual indication of the possibility that the vehicle might roll.
Test functions: The test functions serve to check the coding and to run troubleshooting without the diagnosis tester. This is described in the functional description of the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units
USA: versions of indicator and warning lamps:
The ignition key warning is a function prescribed by legislation in the USA. The intermittent warning tone sounds if the ignition key remains inserted and the driver's door is opened with terminal 15 Off. The warning tone is cancelled by removing the ignition key, by closing the driver's door or after 30 minutes of continuous warning.
The seat-belt warning is activated with terminal 15 On if the belt contact is not closed. The intermittent acoustic warning lasts a maximum of 6 seconds. Thereafter, only the indicator and warning lamp continues to light up.
Gulf States: When the factory-coded legal speed threshold of 120 km/h is exceeded, a single warning tone (limit warning) is issued. The next speed warning can only be triggered when the vehicle travels more than 4 km/h less than the speed threshold. When the limit for the speed warning is reached, the road-speed value displayed in LC display 1 flashes.
Japan: The acoustic reverse warning and acoustic distance warning are output through the external gong,
The diagnosis is described in the functional description of the instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units