Instrument Panel (KOMBI)
Instrument Panel
Instrument panel (KOMBI)
Various instrument clusters are used for the driver's information. These instrument clusters are developed by various suppliers (Continental and Johnson Controls).
NOTICE: Additional fixed indicator lights.
The instrument cluster also has the LIM indicator light. For a speed limit set using the button on the steering wheel, this indicator light illuminates either green on red (exceeded).
Brief component description
The following components are described for the instrument panel:
Instrument panel
The instrument cluster (KOMBI) is connected to the PT-CAN. The front passenger side power distribution box supplies the instrument cluster with terminal 30B. The front electronic module (FEM) supplies the instrument cluster with terminal 30.
The basic version of the instrument cluster has just one plug connection. The high version of the instrument cluster additionally has a MOST interface.
Outside temperature sensor
The outside temperature sensor supplies the value for the ambient temperature to the instrument panel. The ambient temperature is shown on the liquid crystal display. The display resolution is 0.5°C (1°F). The value for ambient temperature is also made available to other control units via the K CAN. The signal from the outside temperature sensor is digitalized in the instrument panel. A calculation model suppresses the effects of thermal radiation from the engine compartment on the signal. At higher driving speeds and lower engine temperatures the system selects lower damping action. The real outside temperature value can only be reliably expected starting at driving speed of about 80 km/h.
Front electronic module (FEM): Front electronic module
The front electronic module (FEM) supplies the instrument cluster with terminal 30 and terminal 30B. The front electronic module (FEM) of the instrument cluster supplies various necessary signals to the PT-CAN.
The following illustration shows the functional networking.
Fuel level sensor
The fuel tank contains two fuel level sensors. Each fuel level sensor sends a signal indicating the amount of fuel in the tank. A value is obtained by adding the two signals. The fuel level sensors are connected to the Rear Electronic Module (REM). The signal is forwarded to the front electronic module (FEM) on the K-CAN2. The FEM transmits the signals to the instrument cluster on the PT-CAN.
NOTICE: Observe repair instructions.
The left-hand fuel level sensor cannot be replaced separately.
Coolant level sensor
The coolant level sensor is a capacitive sensor (no longer a reed contact). The coolant level sensor is supplied with voltage by the front electronic module (FEM) from terminal 15 on (square wave signal 3.3 volts).
The coolant level sensor sends a signal when the coolant level is too low. The information appears in the TFT display in the form of a Check Control message. The coolant level sensor is connected to the front electronic module (FEM). The signal is transmitted to the instrument cluster on the PT-CAN.
Washer fluid level sensor
The washer fluid level sensor is a capacitive sensor (no more reed contact). The washer fluid level sensor is supplied with voltage by the front electronic module (FEM) from terminal 15 on (square wave signal 3.3 volts).
The washer fluid level switch transmits a signal when the washer fluid level is too low. The information appears in the TFT display in the form of a Check Control message. The washer fluid level sensor is connected to the front electronic module (FEM). The signal is transmitted to the instrument cluster on the PT-CAN.
Acoustic sensor
The acoustic sensor in the instrument panel (KOMBI) issues acoustic signals for the following functions:
- Turn indicators
- Hazard warning flashers
The volume varies as a function of vehicle speed.
On-board computer button
The on-board computer button is electrically connected to the steering column switch cluster. The signal is forwarded to the front electronic module (FEM) on the LIN bus. The instrument cluster receives the signal from the FEM control unit on the PT-CAN.
The on-board computer functions can be called up by briefly pressing the on-board computer button on the drop arm. Pressing the on-board computer button again displays the information in the following order:
- Remaining cruising range
- Average fuel consumption
- Average speed
- Distance (with route guidance activated)
- Estimated time of arrival (with route guidance activated)
- Date
- Road sign recognition
System functions
The following system functions are described for the instrument panel:
- Operating readiness
- Operating voltage range
- Outside temperature interference suppression
- Brightness control
- Set speed for the cruise control
- Redundant data storage
Operating readiness
Operational status (operating readiness) depends on the terminal.
- Terminal 30B (basic operation) and terminal 30
The instrument cluster is connected to terminal 30B and terminal 30 via the junction box. The terminal status (Terminal R or Terminal 15) is made available to the instrument panel via the bus system. With Terminal 30 (Terminal R OFF), the instrument panel is in standby mode. Pressing the reset button wakens the instrument panel to display the following: Odometer, time display, ambient temperature, fuel level (can be encoded). The display goes out after 25 seconds.
- Terminal R
With terminal R On, the following are evaluated: Turn signal/high beam switch and fuel level sensor. The time and ambient temperature appear in the TFT display. The on-board computer functions can be started using the on-board computer button (display unlimited in time).
Terminal R is reached automatically once the engine has been stopped.
- Terminal 15
When Terminal 15 is switched ON, a pre-drive check is carried out on the permanent indicator and warning lights.
- Terminal 50 (starter motor)
During the engine start, the vehicle voltage can fall to such a degree that the internal voltage supply (6 Volts) can no longer be maintained. In this case, no analogue signals can be evaluated. No storage processes are run (in the EEPROM) either.
Operating voltage range
The operating voltage range is from 9 to 16 Volts. At a voltage below 7.5 Volts, undervoltage is detected. At a voltage above 16 Volts, no analogue inputs are evaluated.
Outside temperature interference suppression
The computation model in the instrument cluster compensates for effect that the residual heat from the engine compartment has on the outside temperature value. The increase in temperature is delayed. The input variables for the calculation model are:
- Driving speed
- Coolant temperature
- Engine status on or off
- Ambient temperature
A drop in the ambient temperature is adopted and not damped. The engine and the body cannot be colder than the ambient temperature.
NOTICE: Under certain circumstances, an incorrect display of the ambient temperature is physically unavoidable.
Under certain driving conditions, the display deviates from the real value due to damping action. In the event of a customer complaint, this behavior must be explained as the state of the art.
Example for outside temperature compensation:
Motorway driving followed by urban traffic, then stationary traffic
Brightness control
The instrument cluster is illuminated from terminal 15. The status of the vehicle lights and the ambient brightness determine the switch between daytime and night-time illumination. A phototransistor is installed in the instrument panel to calculate the necessary brightness (display, indicator and warning lights, scales, needles).
The brightness value calculated in the instrument panel is transmitted to the bus system (e.g., for the Central Information Display). Dimming can be set individually using the knurled wheel on the light switch. When the vehicle lights are switched on, these individual settings and the phototransistor are used to control the dimming. When the vehicle lights are switched off, the dimming is only controlled by the phototransistor (display brightness according to ambient brightness).
Set speed of the cruise control
The set speed of the cruise control is transferred by the control unit for Integrated Chassis Management (ICM) on the bus system. Cruise control is activated via the steering column switch cluster. The set speed is transferred and displayed with a resolution of 1 kph. The set speed is indicated by a 2 colour marking (needle):
- Green: Cruise control active
- Orange: Cruise control not active
Notes for Service department
General notes
Instrument cluster test functions
The test functions are displayed in the TFT display of the instrument panel. The test functions are used in service to check the encoding. The test functions are also an aid to troubleshooting without the diagnosis system.
Starting the test functions
- Condition: Terminal R on, vehicle stationary, engine switched off.
- At terminal 15 on: Press and hold the reset button in the instrument cluster for 15 seconds until the test function appears (possibly confirm Check Control message first).
- Unlock the blocked test functions with test function 4.
- Unlock by inputting the checksum of the last 5 figures of the vehicle identification number using the reset button.
Terminating the test function
- Terminal 15 or R on
National-market versions
The instrument panel is available in various national-market versions.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.