Instrument cluster: internal test functions, service interval display (SIA), measures for replacing control units

Alongside other functions, the instrument cluster also contains automatic and manual test functions as well as functions for service tasks.

• The Check Control function monitors the bulbs of the vehicle's exterior lighting.
  
• The Predrive Check automatically checks the function of important indicator and warning lamps with terminal 15 On.
  
• The test functions can be used to display coding data and run troubleshooting without a diagnosis tester.
  
• The Service Interval Display (SIA) (oil service or inspection or periodic service) can display and reset data.
  
• Following the replacement of control units - instrument cluster and/or lights switching centre (LSZ) - the vehicle identification number must be matched up.
  

For the checks and settings, all the display options of the instrument cluster are used:

• Pointer instruments
  
• LC display 1 (in the speedometer)
  
• LC display 2 (gear display)
  
• Indicator and warning lamps
  

The functions are described in the functional description of the instrument cluster: 'Displays and functions'.

Brief description of components

K-bus

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.

PT CAN bus

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.

D Bus

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.

byteflight

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.

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 connects as gateway module the PT CAN bus (Powertrain bus), the K bus (Body Electronics bus), the D-bus (diagnostic bus). 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

• Resetting the trip-distance recorder
  
• Operating the SIA reset menu
  
• Setting the time
  
• Operating the test functions
  

Clock symbol button (right):

• Calling up setting time mode
  
• Calling up SIA service date during display of remaining distance
  

Steering-column lever (LSS)

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.

Lights switching centre (LSZ)

The lights switching centre (LSZ) switches the lighting of the instrument cluster and 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.

Main functions

Check Control

The lights switching centre (LSZ) monitors as of terminal 15 On the bulbs of the vehicle's exterior lighting. The lights switching centre (LSZ) reports a lamp fault as a telegram across the K bus to the instrument cluster. The failure of the following bulbs is indicated by the indicator lamp Check Control (lamp fault):

• Full beam, dipped beam headlights, sidelights
  
• Taillights, registration-plate light
  
• Brake light, left and right
  
• Rear fog light, left or right
  

For simplified location of faults, the status is provided via diagnosis and/or test function.

Predrive check

The predrive check is a test for important indicator and warning lamps. With terminal 15 On, the predrive check automatically activates the following indicator and warning lamps.

All the indicator and warning lamps are deactivated together at the end of a fault-free predrive check.

Test functions

The test functions serve to check the coding and to run troubleshooting without the diagnosis tester. The test functions are displayed in the top line of the LC display, display area 1 (distance recorder). The display of the on-board computer function in the bottom line is retained.

NOTE: The test functions can only be run with terminal R On and terminal 15 On with the vehicle stationary and the engine switched off.

The test functions are switched on by

• pressing the S/R button for a longer period (> 5 seconds) with terminal R On and/or terminal 15 On or by
  
• pressing the S/R button and simultaneously switching on terminal R.
  

Test functions 1 and 2 are freely accessible. The following test functions can only be reached after they have been unlocked using test function 19. In test function 19, the display alternates every second between L_on (Lock on = lock) and L_oFF (Lock off = unlock).

To unlock the test function:

Press the S/R button if the display shows L_oFF (Lock off = unlock). The display jumps to test function 0 (Exit test function).

To lock the test function:

Press the S/R button if the display shows L_on. Otherwise, always lock the test functions using test function 19.

NOTE: The test functions are always locked after a terminal change.

Quit test functions:

The test functions are closed

• by switching from terminal R Off or
  
• pressing the S/R button for a longer period or
  
• requesting test function 21.
  

Test function table:

Redundant data storage

The current service interval display data and the kilometre reading are stored in the control unit of the instrument cluster. Parallel to this, the control unit for the instrument cluster transmits this data in cycles across the K bus to the lights switching centre (LSZ) and the electronic vehicle immobilisation unit (EWS) for storage. The data is stored as follows:

• for the odometer, every 100 km,
  
• for the fuel consumption, every 10 litres
  
• for the Service Interval days, every day
  
• with terminal 15 On (RDA status telegram).
  

The redundant data storage means that the data is retained if control units are replaced.

The control unit for the electronic vehicle immobilisation unit (EWS) transfers the data for the new service acceptance concept (KeyReader and SAM 1) to the ignition key.

The control unit for the electronic vehicle immobilisation unit (EWS) has memory capacity (12 blocks of 16 bytes each) for storage of service-relevant data. In the first four blocks, the following data is stored:

• Kilometre reading
  
• Service Interval Display
  
• Vehicle identification number
  
• Upholstery code
  
• Colour code
  

With terminal R On and after verification of the key codes, the first four blocks are transferred onto the key (transponder). When driving, if the data of the Service Interval Display in the EWS changes, the data on the key is also updated. When driving, the kilometre reading is updated on the key every 5 minutes.

KeyReader and Service Acceptance Module 1 (SAM 1)

At service reception, the KeyReader can be used to read out the ignition key. As soon as the ignition key has been inserted, the reader picks up the stored vehicle data. Depending on the vehicle model, the information is shown on a screen using the Service Acceptance Module 1 (SAM 1).

The Service Acceptance Module 1 (SAM 1) can automatically interpret and display the data picked up by the KeyReader and forward it to scheduling and/or order opening.

On the SAM 1 mask SIA IV, only forwarding of the order basis to the downstream system (DMS) is implemented. The following data is displayed in the SAM 1 mask SIA IV:

• Key version
  
• Read-in date
  
• Due (inspection or oil service)
  
• Service remaining distance (in kilometres)
  
• Kilometre reading
  
• Upholstery code
  
• Colour code
  
• Type code
  
• Vehicle identification number
  

Service Interval Display (SIA)

As of terminal R On, the LC display is activated. The Service Interval Display (SIA) appears for 5 seconds in LC display area 1. The Service Interval Display (SIA) displays the functions oil service or inspection or periodic service with the relevant due dates.

When the Service Interval Display is shown, the odometer, the trip distance recorder and the on-board computer functions are hidden.

The outside temperature below 3°C (ice warning) is displayed as soon as the vehicle moves.

The remaining distance is displayed in steps of 50 km (on USA version 25 miles).

Distance-based inspection: A due distance-based inspection is displayed by the messages 'oil service' and 'inspection'. In the case of a distance-based inspection, the remaining distance is displayed. The remaining distance is the real number of kilometres to be driven until the next maintenance interval. If the service interval is exceeded, the remaining distance driven is marked with a minus sign. The display then flashes. When a distance-based inspection is due (oil service or inspection) is calculated from, among other things, the model-related average fuel consumption. For this reason, oil service and inspection can be displayed at the same time under certain circumstances.

Pressing the clock symbol button during the remaining distance display switches the Service Interval Display to the periodic service display.

Periodic service: A periodic service (replacement of brake fluid) is indicated by a clock symbol and a date display (coded date for periodic service with month and year). The next periodic service date is displayed when the clock symbol button is pressed for 5 seconds. If the periodic service is due, the clock symbol lights up in addition to the remaining distance display. The messages 'oil service' and 'inspection' are hidden.

Pressing the clock symbol button switches the display back.

Resetting the Service Interval Display: A service that is due can only be reset using the S/R button via the SIA reset menu of the instrument cluster. Distance-based inspections (oil service or inspection) and periodic services can be individually reset after the minimum consumption quantity and/or minimum interval (days limit) specified in the coding data. A service counter provides information on resetting the Service Interval Display.

NOTE: The service counter is currently not used by the diagnosis.

Resetting the distance-based inspection with S/R button:

1. Ignition key position ”0” (terminal 15 and terminal R OFF)
   
2. Press and hold S/R button
   
3. Turn ignition key to position ”1” (terminal R On)
   Display: test function
   
4. Press button again > 5 seconds (skips test functions)
   Display: Service status SIA OILSERVICE or INSPECTION and remaining distance display
   The distance-based service is displayed with ”Reset” when the coded minimum consumption quantity of 10 litres of fuel has been used and a reset is possible.
   This makes it possible to correct an incorrect sequence of operations (oil service, inspection) as the result of an incorrect reset without having to wait until 1/5 of the consumption value is reached.
   The distance-based service is displayed without ”Reset” when the coded minimum consumption quantity has not been reached and no reset is possible.
   
5. To perform a ”Reset”, press the button for > 5 seconds.
   Display: Service status, ”Reset” flashes for 5 seconds
   
6. Briefly press the S/R button during the flashing phase. The reset is performed.
   Display: The new status is shown for 5 seconds.
   If no reset is required, do not press the S/R button. After flashing 5 times, the old status is displayed for 5 seconds.
   
7. After running through oil service or inspection, the status of the periodic service is displayed.
   
8. If the periodic service is not coded, End SIA is displayed for 2 seconds
   

Resetting the periodic service:

NOTE:

• The sequence for resetting the periodic service is reached via the distance-based inspection .
  
• Between individual resets of the periodic service, 20 days must have elapsed (can be coded).
  
• The periodic service can be brought forward by up to 180 days if an oil service or inspection is due. This allows servicing jobs to be grouped.
  

1. With coded periodic service, the service status is displayed.
   The periodic service is displayed with ”Reset” when the coded days limit is reached.
   
2. To perform a ”Reset”, press the S/R button for > 5 seconds.
   Display: service status flashes
   
3. Briefly press the S/R button during the flashing phase. The reset is performed.
   Display: The new date is shown for 5 seconds.
   If no reset is required, do not press the S/R button. After flashing 5 times, the old date is displayed for 5 seconds. Then
   Display: End SIA for 2 seconds
   
4. If the days limit for reset was not reached, press the S/R button briefly.
   Display: End SIA for 2 seconds
   

Replacing the instrument cluster

The scope of functions of the instrument cluster is determined by the coding data stored in a non-volatile data memory. The coding data is retained even if the voltage supply is disconnected. If the instrument cluster is to be replaced, various measures must be carried out depending on the reasons that led to the replacement. The following four cases show the procedures.

Case 1: The instrument cluster control unit is defective and the light switching centre (LSZ) is OK.

Case 2: The instrument cluster control unit is OK and the light switching centre (LSZ) is defective.

Case 3: The control unit for the instrument cluster and the control unit for the light switching centre (LSZ) must be replaced.

NOTE:

• Only replace control units at the same time if this is unavoidable (stored total odometer reading is irretrievably lost).
  
• Disconnect battery!
  

Case 4: As a check, replace the control unit for the instrument cluster or the light switching centre control unit (LSZ).

NOTE: Although exchanging one of the two control units as a test is possible in principle, it should be avoided wherever possible.

NOTE: Simultaneous replacement of the instrument cluster and lights switching centre (LSZ) should be avoided. The total odometer reading (mileage) is irretrievably lost.

Car and Key Memory

Display of the Car Memory functions:

Notes for Service department

• When the instrument cluster is replaced, the mileage is re-imported by the lights switching centre (LSZ) and the original kilometre reading / mileage is recovered.
  NOTE: This function is only permitted with new parts < 255 km.
  

• The following functions are described in the functional description of the instrument cluster: 'Displays and functions'
  - Redundant data storage
  - Brightness control of the instrument cluster
  

Country-specific version

In the case of vehicles for the markets USA, Canada and Japan, only the remaining distance is displayed in the SIA. The periodic service has been coded out; the clock symbol does not appear.

Diagnosis

On the E85, DS2 (diagnosis interface 2) is used as the diagnosis language for diagnosis communication. So that control units that use KWP2000 (Key Word Protocol 2000) for diagnosis can be used, the E85 has KWP2000*.

KWP2000 is a protocol for diagnosis standardised by the automobile industry.

In KWP2000*, KWP2000 has been integrated in the diagrams of the DS2.