Base Instrument Cluster: Notes

The base instrument cluster differs from the high version cluster by lack of the IKE. All processing is performed internally in the cluster. Also, there is no Check Control display matrix, but rather a check control pictogram.

The cluster consists of five analog gauges. The processing electronics and drivers for the gauges are contained in the cluster. The five gauges include:

Fuel Gauge
Speedometer
Tachometer
Fuel Economy Gauge
Coolant Temperature

Fig 1: Identifying Base Instrument Cluster

Courtesy of BMW OF NORTH AMERICA, INC.

Three Liquid Crystal Display blocks are provided for the:

Check Control Display - pictogram
Mileage, Outside Temperature and BC Display
Transmission Range and SI Display

Warning lamps and indicators are positioned to the left and right of the display blocks. The number of warning lamps is greater on the base cluster for the display of several check control warnings. All of the warning lamps and indicators are LEDs and not replaceable.

Critical warning lamps use two LEDs for a safety margin.

There are replaceable lamps for the back lighting on the liquid crystal display units.

The Left Display Block contains a pictogram for various check control warnings. LED's within the display will illuminate for:

Lighting failures for headlight (low beam), taillight and brake lights.
Open doors or trunk
Low washer fluid

Fig 2: Identifying Left Display Block (Pictogram For Various Check Control Warnings)

Courtesy of BMW OF NORTH AMERICA, INC.

Additional circuits monitored by check control include the oil level and transmission emergency program. These warnings are indicated by lamps positioned in both indicator display areas on the left and right sides on the bottom of the instrument cluster.

Due to the ability to illuminate multiple warning LEDs, there is no priority displays for the pictogram check control. If multiple faults exist, each corresponding LED will illuminate.

The LED will remain illuminated as long as the fault exists. The only exception is the washer fluid which will go out 60 seconds after KL 15 is switched ON.

All check control and lamp control circuits are monitored by the Light Check Module (LCM). When failures or faults exist, the messages are passed to the cluster for display over the K-Bus.

The Middle Block contains the displays for the Total Mileage, Trip Mileage and Board Computer.

The total mileage is stored in non-volatile memories in the cluster EEPROM and the LCM.

Fig 3: Identifying Total Mileage Display

Courtesy of BMW OF NORTH AMERICA, INC.

The mileage can be displayed with the key off for 25 seconds if the mileage reset button is pressed.

Board Computer information can be displayed by pressing the turn signal lever.

NOTE: The outside temperature is displayed automatically every time the key is switched ON.

The Right Block contains the displays for the automatic transmission driving range and the Service Interval Indicator III.

The display of the Service Indicator on the E39 is the same as previous systems. The processor for the intervals is located in the cluster electronics. However, the processing method for determining interval times has changed. The E39 uses the new Service Interval III system. Interval times are based on fuel consumption instead of mileage and starts. This system was introduced on the 1996 E38 750iL was subsequently phased into the other models.

Using fuel consumption offers several advantages over the previous method for determining oil service.

Fig 4: Identifying Right Block Display

Courtesy of BMW OF NORTH AMERICA, INC.

First, the processing electronics are less involved in that only one value is needed for the processing.
Second, the use of fuel consumption is a more accurate method of determining engine load and the need for service.
Third, resetting of the indicator before the scheduled time will not effect the time to the next service.

A set volume of fuel (in liters) is stored in the EEPROM of the SI. The volume of fuel is dependent on the vehicle and engine size. The processor receives the "ti" signal as the vehicle is used. As 20% of the stored volume is consumed, one of the green LEDs will go out. Each successive 20% of fuel consumption will cause the next LED to go out until 100% of the stored volume has been consumed. At this point the yellow LED will come on indicating the service is due. At 108% of the volume, the RED LED will illuminate indicating an over due service.

With every reset, the total volume of fuel is restored in the EEPROM and the calculation starts over again.

Fig 5: Identifying TI Signal

Courtesy of BMW OF NORTH AMERICA, INC.