Instrument Cluster (Basic)

General

At series launch, the instrument cluster (basic) features two bus interfaces which enable the information link (data link/serial) to the connected control units.

These busses are:

• K-bus (body bus)
  
• Diagnosis bus (link to diagnostic socket).
  

A further bus interface provides the link to the automatic transmission unless the instrument cluster has a CAN interface. On manual transmission vehicles, the reverse gear selector status is read in via this connection.

Coded data determining the scope of functions of the instrument cluster are stored in a non-volatile data memory (data is retained when supply voltage is disconnected).

The various scope of functions includes, for example, the vehicle model and the country language variant.

Replacing Instrument Cluster

The four cases described in the following show under which circumstances which steps must be taken to ensure correct replacement of the instrument cluster electronics.

Case 1: The instrument cluster control unit is defective and the light check module control module (LCM) is OK.

Case 2: The instrument cluster control unit is OK. and the light check module control module (LCM) is defective.

Case 3: The control unit for the instrument cluster and the control unit for the light check module (LCM) must be replaced.

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

Note

Disconnect battery!

Case 4: As a check, replace the control unit for the instrument cluster or the light check module control unit (LCM).

Note

Although exchanging one of the two control units is possible in principle, it should be avoided wherever possible.

Scope of function

The following are displayed or used for a function:

Test functions

The test functions which could be called up on the on-board computer in previous series can now be called up in the instrument cluster.

System test (test No. 2): The system test is used to test the display unit together with its elements which can be controlled from the instrument cluster.

These elements are:

• All pointer instruments
  
• All LC displays with a segment test and their background lighting
  

Indicator and warning lamps for:

• Belt warning
  
• Fuel reserve
  
• General brake warning lamp
  
• Parking brake
  
• Left and right turn signal indicators
  
• Front and rear fog light
  
• High beam
  
• Gear indicator (automatic transmission)
  
• Service interval display SIA
  
• Check control displays (if coded)
  
• Air suspension
  
• Fault automatic transmission
  
• Engine oil level
  

Pointer instruments: During the system test, operation of the pointer instruments is diagnosed and a corresponding fault code is set in the fault code memory if an electrical fault occurs. In addition, particular care must be taken to observe whether the pointers move smoothly and continuously over their entire indication range during the first test pass. During the second pass within a system test sequence, the pointer instruments are not moved continuously and smoothly over their entire indication range. In this case, the electrical drive data is measured at various indication angles of the pointers.

Selecting test functions:

All test functions, apart from test numbers one and two, are interlocked and must be released by means of test function number nineteen.

Procedure: Press and hold (approx. 5 s) the trip recorder reset button (left-hand button in the instrument cluster) with terminal R "ON" until "__tESt__1._" appears in the instrument cluster display. The corresponding test (system test corresponds to test 2 "__tESt__2._") can be selected by pressing/releasing the button again within 1 second. The first subfunction of the test selected then appears after approx. 1 second. The subfunction (the system test has no further subfunction) of the corresponding test can be selected by pressing the button again. Since there are no further subfunctions associated with test 2 (system test), the system test is triggered after the "__tESt__2.0" display appears and the trip recorder button is pressed. If the test is a locked test (test 3 to 21) the lock is released by pressing the trip recorder button when "_L_oFF" appears in the display. The display then jumps to test 0 so that the corresponding test can be selected by briefly pressing the button.

Test function 20 Correction factor for the “average fuel consumption function”.

Test function 20 has 4 subfunctions 20.0 (indicates the stored correction factor), 20.1 (enables setting of the units decimal position), 20.2 (enables setting of the tens decimal position) and 20.3 (enables setting of the hundreds and thousands decimal position where here only the number pairs 07, 08, 09, 10, 11 and 12 are possible. The adjustment range of the correction factor is defined from 0750 to 1250. The factor must be set to 1000 (factory setting) in order to carry out a correction otherwise it will not be possible to calculate a new factor with the formula. When the factor is set to 1000, a new correction factor is derived from the actual consumption in litres per 100 km divided by the displayed consumption in litres per 100 km multiplied by 1000. If other units of measure are displayed, i.e. miles, litres or miles per gallon and kilometres per litre these units of measure must be converted into litres per 100 km for the purpose of calculating the correction factor. This new factor can now be set with the subfunctions 20.1 to 20.3.

To select test function 20: Press and hold (approx. 5 s) the trip recorder reset button (left-hand button in the instrument cluster) with terminal R "ON" until "__tESt__1._" appears in the instrument cluster display. Test 20 can be selected by repeatedly pressing/releasing the button within 1 second. The first subfunction of the test selected then appears after approx. 1 second. The subfunction of the corresponding test can be selected by pressing the button again. The set correction factor is indicated in test function 20, subfunction 0 (20.0). The units decimal position is counted down (0-9) by switching to subfunction 20.1. The units decimal position continues changing automatically until the next subfunction is selected. The position last displayed is adopted in the correction factor. The same procedure also applies to subfunction 20.2 which counts down the tens decimal position (0-9). The hundreds and thousands decimal position are counted down in subfunction 20.3 where only the digit pairs 07, 08, 09, 10, 11 and 12 are shown so as to maintain the valid range for the correction factor from 750 to 1250.

Speed display

The speed display is equipped with various types of speedometer depending on the vehicle model.

The instrument cluster receives the position signal tw from the antilock brake system (ABS)/automatic stability control (ASC)/dynamic stability control (DSC) control unit. The instrument cluster uses this to control the speedometer, total odometer reading and trip recorder reading displays.

The instrument cluster derives the speed from the position signal tw and from the position pulse number (K-number) stored as coding data in the instrument cluster. In addition, the instrument cluster provides a speed signal (Speed-A ) for the connected control units. The speed information is provided in the form of a telegram on the body bus (K-bus ).

Engine speed display

The instrument cluster uses the engine speed signal from the engine control unit (td for petrol engines) to determine the engine speed. Adaptation to the various types of engines uses the stored coding data.

From terminal 15 "ON", the engine speed instrument (rev counter) is controlled by the instrument cluster with the corresponding engine speed signal. The engine speed information is also provided on the body bus (K-bus) for other control units.

Phased-in as from 9/97, the instrument cluster is equipped with a CAN connection. Coding data defines whether the engine speed signal is routed via the CAN bus or via a separate line to the instrument cluster.

Fuel consumption display

The fuel consumption signal t_KVA is derived from the injection signal supplied by the engine control unit. In combination with the position signal, it yields to the consumption per unit of distance (e.g. l/100 km).

The fuel consumption signal t_KVA is not only used for calculating the fuel consumption but also for controlling the service interval display and therefore displaying the service interval.

Phased-in as from 9/97, the instrument cluster is equipped with a CAN connection. Coding data defines whether the fuel consumption signal is routed via the CAN bus or via a separate line to the instrument cluster.

Fuel gauge

The tank content is measured by two lever sensors which are separately linked to the instrument cluster. Each lever sensor is connected by a separate ground (analog ground) and a sensor line (analog positive) to the instrument cluster. There is no reserve contact in the level sensor to activate the fuel reserve warning lamp. The fuel reserve warning lamp is switched as a function of the tank contents by comparison with a reserve threshold value.

The "fuel reserve" signal is output as information for engine management. It is coupled to the fuel reserve warning lamp and is switched on for 2 seconds as a function check when terminal 15 is switched on (predrive check).

The different methods of determining the fuel level for each tank half is determined by means of the coding data.

Coolant temperature display

The instrument cluster determines the current coolant temperature from the coolant temperature sensor (NTC resistor). The coolant temperature sensor is connected by a separate ground (analog ground) and a sensor line (analog positive) to the instrument cluster.

The instrument cluster places the "coolant temperature" information on the body bus (K-bus) for other systems.

Phased-in as from 9/97, the instrument cluster is equipped with a CAN connection. Coding data defines whether the coolant temperature signal is routed via the CAN bus or via a separate line with separate coolant temperature sensor to the instrument cluster.

Service interval display

The service interval display (SIA) is an indication to the driver and the workshop that an engine oil service, distance-dependent services or time-dependent service. The service intervals of the vehicle are related to the consumption. The current service interval status is displayed from terminal 15 "ON" for 10 seconds after a minimum engine speed of 400 rpm is reached.

The service interval display (SIA) data is also stored in the light check module (LCM ).

Reset service interval display

The service interval display (SIA) is reset by pulses of defined length at the service interval reset input. Each reset procedure can be carried out individually (service interval display [SIA] reset). The oil service, time-dependent service and/or distance-dependent service can be reset.

Total odometer reading

Display of the total distance covered is a component part of the LC display. The current mileage is indicated on the display from terminal R "ON". With terminal R "OFF", pressing and releasing the trip recorder reset button displays the mileage for approx. 25 seconds. The unit of distance (km/miles) dependent on the coded country-specific version is displayed between the total distance recorder and the trip recorder. The total distance is placed on the body bus as a telegram (K-bus).

The total distance is stored in the instrument cluster and in the light check module (LCM). "999999" is displayed as the total distance if the instrument cluster cannot read the total distance and it cannot be determined by way of the light check module (LCM).

Trip recorder reading

Display of the distance covered on a trip is a component part of the LC display. The current trip recorder reading is shown on the display from terminal R "ON". At terminal R "OFF", pressing and releasing the instrument cluster button displays the mileage for approx. 25 seconds. The unit of distance (km/miles) dependent on the coded country-specific version is displayed between the total distance recorder and the trip recorder.

Outside temperature display

The instrument cluster determines the current outside temperature using the outside temperature sensor (NTC resistor). The outside temperature sensor is connected by a separate ground (analog ground) and a sensor line (analog positive) to the instrument cluster. The outside temperature is displayed permanently in the instrument cluster. If the outside temperature drops below +3^o C while the car is being driven, dependent on the coding, a warning tone (gong or beep for ice warning dependent on coding) is triggered and the displayed value flashes.

The display unit (^oC/^o F) is determined in the coding data. However, it is possible (as of diagnosis index 31, refer to "diagnosis program", "instrument cluster", "identification") to change the display unit from ^oC to ^o F and from ^oF to ^oC. For this purpose the ignition lock must be switched from position "1" (terminal "R") to position "0" (terminal "15" and terminal "R" OFF) with the trip recorder reset button pressed. The displayed temperature unit is changed after releasing the trip recorder reset button and as of ignition lock position "1" (terminal "R"). The unit display selected is retained for as long as supply voltage is applied to the instrument cluster and no reset is triggered.

The display ranges from -40^oC to +50^oC. A rise in the outside temperature is damped in the display in order to avoid displaying an incorrect outside temperature due to the influences of radiated engine heat and other ambient conditions. A drop in the outside temperature is not damped.

The instrument cluster sends the "outside temperature" information via the body bus (K-Bus). In ignition lock position "0", the outside temperature sensor is read by the instrument cluster at time intervals which are within the minute range. For this purpose, the instrument cluster is temporarily activated, provides the information and then switches itself off again.

Visual LC displays

General

The back lighting of all LC display fields is provided by LEDs. The LEDs provide the back lighting for the service interval display (SIA) field together with gear display, total odometer with trip recorder and outside temperature or functions of the on-board computer display and the field for check control messages.

On-board computer functions

If no on-board computer functions are provided and coded, the instrument cluster (basic) only features the outside temperature display instead.

Check-control messages

As optional equipment (standard in certain models), the instrument cluster (basic) features an LC display field for check-control messages. The back lighting of the vehicle symbol is only switched on by the light check module when a check-control message is present. Light faults for left and right low beam, left and right reversing light, left and right brake light are displayed in the LC display field for check-control messages. In the case of a defective brake light switch, both brake lights are indicated as a light fault. If the centre brake light is defective, the light check module sets the symbol for the right-hand brake light. Light fault statuses occurring simultaneously are displayed in parallel.

The "top up wash water" message is also displayed in the form of a pictogram in the display field for the check-control messages. The light fault messages and the "top up wash water" message are sent by the light check module via the body bus (K-bus) to the instrument cluster. The "top up wash water" message has a priority status in the display system. When the message is received, it is retained until the next terminal 15 "OFF" and goes out after 60 seconds. The message is only re-evaluated at the next terminal 15 "ON".

The four doors and the boot/trunk lid can be displayed separately for the "door open" message. These messages are sent on the body bus (K-bus) from the basic module to the instrument cluster.

Instrument dimming

The brightness of the LC display fields is controlled by a phototransistor. When the vehicle lights are switched on, the brightness is controlled by the phototransistor and the dimmer setting.

The light-check module (LCM) sends the dimmer setting for the instrument lights and the indicator lamps as a telegram on the body bus (K-bus) and via line 58g as a power signal to the instrument cluster.

Acoustic indicator

Monitoring turn signal indicator lamps

The turn signal indicator lamps are monitored the switching noise of an encapsulated relay operating synchronously with the turn signal indicator lamps.

Light warning

The light warning is provided only acoustically. The relay installed in the instrument cluster monitoring the turn signal indicator lamps is also used for the light warning. The light warning sounds for 8 cycles each of approx. 0.5 seconds continuous tone at approx. 64 Hz and a subsequent 0.5 second pause when the driver's door is opened for the first time and when the parking lights are switched on. During the light warning, the turn signal indicator lamps are only monitored by means of the indicator lamps.

Seat belt warning

The acoustic seat belt warning is dependent on the coded data and is controlled by the light check module using a telegram sent on the body bus (K-bus) to the instrument cluster. When the seat belt warning is triggered, the gong tone 3 (T3) is activated for a maximum of 6 seconds with pauses of approx. 1.3 seconds.

Ignition key warning

The acoustic ignition key warning is dependent on the coded data and is controlled by the light check module using a telegram sent on the body bus (K-bus) to the instrument cluster. When the ignition key warning is triggered, the gong tone 3 (T3) is activated for a maximum of 60 seconds with pauses of approx. 1.3 seconds.

Temperature warning

The acoustic outside temperature warning is controlled as a function of the temperature detected by the outside temperature sensor. If the temperature drops below a threshold of +3^oC, a warning tone sounds in the basic instrument cluster at approx. 2 kHz generated by a beeper built into the instrument cluster.

In the case of an instrument cluster with on-board computer functions, the temperature warning is provided by a short gong tone 3 (T3).

Speed warning

The speed warning is dependent on the coded data where the speed value, at which the warning is to be activated is defined by the coding program. The speed warning is a legal requirement for the "Gulf State" country-specific version.

Speed signal speed-A

The instrument cluster receives the position signal tw from the antilock brake system (ABS)/automatic stability control (ASC)/dynamic stability control (DSC) control unit.

The instrument cluster derives the speed signal (Speed -A) from the position signal tw and from the position pulse number (K-number) stored as coding data in the instrument cluster.

The speed signal (Speed-A) is provided as a signal output for connected control units. The road speed information for the speedometer A-signal is received by the connected control units by measuring the frequency or period duration. This speed information is placed on the body bus (K-bus) as a telegram.

Reverse gear detection (manual transmission)

The "Reverse gear detection" function is only active if this function is correspondingly coded in the instrument cluster. If the instrument cluster is coded for manual transmission, the program and selector lever display for automatic transmission is masked out.

The "reverse gear engaged" information is made available in the form of a telegram via the body bus (K-bus).

Transmission program display (automatic transmission)

If the instrument cluster is coded for automatic transmission, the program and selector lever display for automatic transmission is activated.

The instrument cluster is connected to the transmission control unit by means of a separate data link. By way of this data link, the transmission control unit informs the instrument cluster which drive range is engaged, which drive program is switched on and whether the transmission is in the emergency program. If reverse is engaged, the message is placed on the K-bus.

Body bus (K-bus)

The body bus (K-bus) is one of the two information links (data link/serial) via a data link to other control units. The body bus is only monitored electrically by the instrument cluster. The body bus is monitored by the basic module (GM). The instrument cluster is also responsible for linking the:

• K-bus (body bus)
  
• Diagnosis bus (link to diagnostic socket),
  

bus systems together (gateway function).

Diagnosis bus (D bus)

The diagnosis bus (D-bus) is one of two information links (data link/serial) via two data links to the control units with diagnostic capabilities. The diagnosis bus is only active when a BMW service test system is connected to the diagnostic socket.

Warning lamps

General: The back lighting of all warning lamp symbols and the automatic transmission range engaged together with the drive program selected is provided by LEDs.

General brake warning lamp: The warning lamp can be switched on by the light check module (LCM) when, for example, the LCM detects that the brake fluid level is low or the instrument cluster detects that the brake pad sensor loop has a break to ground. The warning lamp is also switched on after ignition "ON" as a function check (predrive check) and goes out when a minimum engine speed of 400 rpm is exceeded.

Seat belt indicator lamp: The seat belt indicator lamp is activated dependent on the coding data. For vehicles without a seat belt buckle contact, it is switched on for approx. 6 seconds after terminal 15 "ON".

On vehicles equipped with a seat belt buckle contact, the warning lamp is switched on from terminal 15 "ON" by a corresponding K-bus telegram from the light check module (LCM) until the seat belt contact is opened (seat belt buckle latched in position).

Fuel reserve lamp: The fuel reserve warning lamp is not switched by a reserve contact in the level sensor. It is switched as a function of the tank contents by comparison with a reserve threshold value.

The "fuel reserve" signal is output as information for engine management. It is coupled to the fuel reserve warning lamp and is switched on for 2 seconds as a function check when terminal 15 is switched on (predrive check).

Turn signal indicator lamps: The turn signal indicator lamps are switched by means of a corresponding K-bus telegram from the light check module (LCM) to the instrument cluster.

Fog light indicator lamp: The fog light indicator lamp is switched by means of a corresponding K-bus telegram from the light check module (LCM) to the instrument cluster.

Rear fog light indicator lamp: The rear fog light indicator lamp is switched by means of a corresponding K-bus telegram from the light check module (LCM) to the instrument cluster.

High beam indicator lamp: The high beam indicator lamp is switched by means of a corresponding K-bus telegram from the light check module (LCM) to the instrument cluster.

Oil level warning lamp: The warning lamp is switched by means of a corresponding K-bus telegram from the light check module (LCM) to the instrument cluster.

As a function check, the warning lamp is switched on for 2 seconds when terminal 15 is switched on (predrive check).

Air suspension: If coded, the warning lamp is switched by means of a corresponding K-bus telegram from the air suspension control unit (EHC) to the instrument cluster.

If coded, the warning lamp is switched on for 2 seconds as a function check when terminal 15 is switched on (predrive check).

Air suspension: If coded, the warning lamp is switched by means of a corresponding K-bus telegram from the air suspension control unit (EHC) to the instrument cluster.

Transmission fault: If automatic transmission is coded, the warning lamp is switched by means of a corresponding telegram (150 Baud) from the automatic transmission control unit. By way of this data link, the instrument cluster is also informed of the drive range engaged to display the appropriate range.

Note

The indicator lamps listed in the following are controlled directly via corresponding connector pins by the relevant system.

Oil pressure indicator lamp: The warning lamp is switched by the oil pressure switch.

Battery charge indicator lamp: The warning lamp is switched by the D+ terminal 61 signal (charge mode approximately system voltage) to the instrument cluster.

Parking brake warning lamp: The warning lamp is activated by a switch on the parking brake. The switch is open when the parking brake is released.

As a function check, the warning lamp is switched on for 2 seconds when terminal 15 is switched on (predrive check).

Airbag indicator lamp: The warning lamp is switched by a signal (ground) from the airbag control unit.

Antilock brake system indicator lamp: The warning lamp is switch by the ABS control unit. Since the warning lamp must light in the case of a signal line failure a second signal input is provided in the instrument cluster for this warning lamp. In the case of this new ABS control unit, this second line must be connected to ground for the ABS warning lamp to light. The new function, signal line high (system voltage) warning lamp active, signal line low (ground) warning lamp off and signal line high (high-ohmic, interrupted) warning lamp active, also takes into account a break in the signal line. The previous function, signal line high (high-ohmic) warning lamp off and signal line low (ground) warning lamp active is still possible.

Catalytic converter indicator lamp (country version Japan): The "catalytic converter overheating" warning lamp is switched by a signal (ground) from a thermal switch on the exhaust gas cleaning system.

Check engine (exhaust gas warning lamp): The "check engine" warning lamp is switched by a signal (ground) from the engine control unit.

Preheat indicator lamp (diesel): The warning lamp "preheat" is switched by a signal (ground) from the engine control unit.

Cruise control active indicator: The "cruise control active indicator" is switched by a signal (ground) from the cruise control unit or by the engine control unit for diesel engines.

Check engine (exhaust gas warning lamp): The "ASC" warning lamp is switched by a signal (ground) from the engine control unit. The warning lamp is switched on statically if the ASC is switched off. When the ASC is switched on, the warning lamp goes out after a function check (predrive check) and flashes during a control phase.

As a function check, the warning lamp is switched on for 2 seconds when terminal 15 is switched on (predrive check).