Instrument Cluster (Basic) - Part 2 of 2
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 degree 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 (degree C/degree 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 degree C to degree F and from degree F to degree C. 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 degree C to +50 degree C. 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 center 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 trunk/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 degree C, 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 module.
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 modules. The road speed information for the speedometer A-signal is received by the connected control modules 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 module by means of a separate data link. By way of this data link, the transmission control module 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 modules. 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 modules 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 too 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 module (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 module (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 module. 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 module.
Antilock brake system indicator lamp: The warning lamp is switch by the ABS control module. 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 module, 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 module.
Preheat indicator lamp (diesel): The warning lamp "preheat" is switched by a signal (ground) from the engine control module.
Cruise control active indicator: The "cruise control active indicator" is switched by a signal (ground) from the cruise control module or by the engine control module for diesel engines.
Check engine (exhaust gas warning lamp): The "ASC" warning lamp is switched by a signal (ground) from the engine control module. 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).