Trip Computer: Description and Operation
Description of the On-Board Computer IVAn expanded version of the On-Board Computer III is standard equipment on the E32 and E34.
Additional functions of the OBC IV are:
- Estimated time of arrival.
- Distance traveled.
- Metric/U.S. Standards measurement displays.
- Control of the "Parked Car Ventilation System" (if equipped).
OBC information is now displayed in the Check Control (CC) display without a simultaneous OBC display change. This gives the driver two independent displays where the information of his choice can be recalled.
The language of the OBC is now changed when the Check Control language is changed.
All of the buttons have an illuminated strip whenever the lights are turned on for easier usage in the dark.
Block Circuit Diagram
The order and number of OBC displays shown in the CC display may be selected in any sequence.
Numerical input may be done in any order using the 1000, 100, 10 and 1 buttons. Each time a button is pressed the value of that digit increases by 1. When a 9 is selected, a 0 will follow when the button is pressed again. If one of these buttons is held down the digit will automatically increase by 1 every .5 second.
In ignition position 0 the time or date will be displayed if that button is pressed. Other functions are only possible in position 1.
In the event of a loss of battery power to the OBC module, all data stored will be lost except for CODE (if one was entered).
A photo-transistor automatically varies the brightness of the LCD display in accordance to the overall light level in the car.
LED's are provided as reminders when these functions are selected; TIMER, M MPH, CODE.
The OBC module also controls a chime to bring attention to certain displays, and power to the Motronic Control Unit in the CODE function.
Diagnosis and Repair
Faults are stored in the OBC module for diagnosis with the BMW Service Tester. Input signals and button operation on the OBC panel can also be checked with the BMW Service Tester.
Coding Plug
Coding plugs for different country variations and model differences are available to enable the use of one module for various applications.
To check for proper coding plug installation press the 1 and 100 buttons at the same time with the ignition in position 1 or 2. For a U.S. model E32 the display should read: 7 07 TYP
If the display should read PPPP, this means that the module cannot read the coding plug information. This could mean that the coding plug is defective or possibly not fully plugged in.
LANGUAGE
The OBC language is now changed whenever the Check Control language is changed. A total of six languages can be chosen in this order: English U.S., German, English U.K., French, Italian and Spanish.
Language change
To change languages follow this procedure:
1. Turn ignition key to position 1.
2. Hold CC button down until the next language appears (approx. 10 seconds). Release button.
3. Repeat this process until the desired language appears.
The newly selected language will be stored unless battery voltage is taken away from the CCM.
In this event the primary language, ENGLISH U.S., as programmed in the coding plug of the instrument cluster, will re-appear when battery voltage is restored.
UNITS OF MEASUREMENT CHANGE
By pressing the changeover button the displays will change from U.S. standards to metric units. Pressing the button again will bring back the U.S. standards. This can be helpful when traveling outside the United States in a country that uses the metric system of measurements.
OBC INPUTS AND DISPLAYS
HR/DATE (hour/date)
Pushing this button repeatedly displays the time and date alternately. Leap years are now accounted for, eliminating resetting on those occasions.
Changes may be made to the time display when the HR function is selected by pushing the numeric buttons. This new time is not accepted until the S/R button is pushed. The original time will be retained unless the S/R button is pushed. The same applies to the date function.
An hourly reminder of 3 soundings of the chime may be selected or deactivated by selecting the HR function and the S/R button. A "sound" symbol will be displayed on the OBC when this has been selected.
TEMP (temperature display)
A PTC resistor-type sensor supplies a signal to the OBC module. Display range is from -22°F to +122°F. A gong is sounded when the temperature drops below +37°F. The display also flashes for a period of 8 seconds. The gong is triggered again when reaching +37°F if the temperature rose above +42°F since the chime sounded.
The sensor is located next to the right front fog light. Input from the sensor is not accepted by the OBC module with the car at a standstill.
If the sensor should fail the display will read a constant -22°F.
Distance pulse sensor (vehicle speed input)
Signal comes from the speed sensor located in the rear differential housing via the electronic speedometer.
AVG MPG (fuel consumption)
Average fuel consumption is calculated by comparing a voltage signal received from the Motronic ECU against the load speed signal. The voltage signal from the Motronic ECU varies upon the opening time of the fuel injectors.
OBC IV allows the customer to monitor two separate fuel consumption periods. This is done by pressing the AVG MPG button. The display will alternate between AVG MPG 1 and AVG MPG 2.
To reset, select the appropriate AVG MPG mode and press the S/R (set/reset) button.
A customer may find this beneficial on a trip to 1) monitor fuel consumption of the entire trip and 2) using the second AVG MPG function to monitor fuel consumption per tankful.
Fuel Tank Level
A variable resistor sends a signal to the OBC module according to the fuel level in the tank.
The module needs no calibration for level (as on OBC II) due to the fuel tank information on the coding plug.
A separate low fuel level warning light contact is provided and is separate from the variable resistor.
AVG MPH (average speed)
This function gives the average speed from the last time the S/R button was pressed while in this function. A new average is calculated when pushing the S/R button after the AVG MPH button has been selected.
M MPH (speed limit warning)
This function allows the driver to be informed by a chime and flashing LED that the programmed speed selected has been exceeded.
To select a speed at which this warning is sounded simply input it using the numeric buttons while in this mode. If the speed the vehicle is traveling is also the speed at which the warning is to be given, push the M MPH button followed by the SIR button.
The chime also sounds if the vehicle speed drops 3 mph below the programmed speed.
RANGE
This display shows an approximate mileage that the car can cover on the remaining fuel in the tank.
This is done automatically without any input from the driver. The ignition must be turned to either position 1 or 0 while refueling for a new calculation to start. No new display is shown until 4 minutes after refueling. If the fuel level is at the top of the tank a + sign appears in the displays.
CODE
This function may be used as a theft deterrent as it blocks the voltage supply to the Motronic Control Unit.
Procedure for setting code:
1) Ignition in position 1.
2) Press CODE button.
3) Input code using numeric buttons. (Code can be cancelled at this time by turning the ignition to position 2.)
4) Press S/R button - code is now set. When ignition is turned to position 0 the CODE LED will be illuminated for 36 hours. If the LED flashes for the first 10 seconds this indicates that the hood contact is not closed.
With a code set, three attempts are given to start the car before a horn is sounded for 30 seconds.
Procedure for cancelling code and starting car:
1) Turn ignition to position 1 or 2.
2) The OBC display will flash the word CODE.
3) Input correct code with numeric buttons.
4) Car can now be started while retaining the same code number until code is set again; or
5) Code may be cancelled by pressing the S/R button.
NOTE: Code is retained even when the battery has been disconnected!
Emergency deactivation of CODE function
If the code has been forgotten this procedure must be followed to deactivate it.
1) Disconnect and then reconnect the battery.
2) Turn ignition to position 1; alarm will sound.
3) A time of 15 minutes will now be displayed on the OBC; this will count down.
4) After 15 minutes the engine can be started.
S/R (set/reset)
This button is used to start the calculation of these functions when they are selected.
- average speed;
- average fuel consumption; and
- timer (stopwatch function).
TIMER
On the 735i (without "Parked Car Ventilation System") this function serves as a stopwatch. It is activated by pushing the TIMER and then the S/R button. An LED on the TIMER button is illuminated at this time. TIMER function is stopped by pushing the S/R button while in this mode.
To obtain an intermediate time while in TIMER mode, simply press the TIMER button. The TIMER LED will now flash. Push the TIMER button again to return to the ongoing time.
On the 750iL (with "Parked Car Ventilation System") this function serves as a timed switch to turn ON and OFF the "Parked Car Ventilation System".
When the Ventilation System is activated, it automatically runs for a period of 30 minutes.
NOTE: The Ventilation System will only operate if the outside temperature is above 60°F (16°C) and the ignition is OFF.
To program switch-on times follow this procedure:
- Turn ignition to position 1.
- Press TIMER button twice (T1 will be displayed).
- Select desired switch-on time.
- Press S/R button (left TIMER LED will light).
- Press TIMER button again to select a 2nd switch-on time (T2 will be displayed).
- Select desired switch-on time.
- Press S/R button (right TIMER LED will light).
These times will remain unless written over with new ones.
To deactivate the automatic switch-on times select the TIMER mode (T1 or T2) and press S/R. The appropriate LED will go out.
While the Ventilation System is activated, the appropriate LED will flash.
The Ventilation System will be turned OFF if the ignition is turned to positions 1 or 2. IF an immediate switch-on of the Ventilation System is requested, turn the ignition to "ACC", Press TIMER and S/R. The system will now run for 30 minutes or until the ignition is turned to the "RUN" position.
To operate the Ventilation System if temperatures are below 60°F (16°C), for testing purposes, press TIMER and TEMP together until the system turns ON (approx. 5 seconds).
DIST (distance to destination)
After the input of mileage, this function allows the customer to see how many miles he has left to travel until that mileage input is reached.
To input a mileage, press DIST, input the mileage, then press S/R. To see how many miles are then left to go, press DIST. If the mileage amount is exceeded from what was input a minus sign will be shown in the display.
ARR (estimated time of arrival)
Once a mileage has been entered into the DIST mode, the ARR button can be pushed to display an estimated time of arrival. This is based on the average speed of the vehicle.
On-Board Computer Displays
The OBC displays can now be called up on the CC display panel. This is only possible if there are no CC displays present. This function is automatic while pressing in on the end of the turn signal switch. This also will scroll through the OBC displays one by one as on OBC II. The last selected display remains on the CC display until one of the information buttons on the OBC is pressed.
It is possible to select the order in which OBC information is shown on the CC display. By pushing in on the turn signal switch for 3 seconds the CC display will indicate PROGRAM 1. You may then select the OBC displays to be shown in any order. The buttons selected should be held down until the CC display shows this selection by number. The SET/RES button must then be pushed to record this program. The original program can be recalled by simply pushing in the turn signal switch for 3 seconds and then the SET/RES button.
If only one of the AVG MPG or TIMER modes is desired in the Check Control display, press the S/R button after pressing that function button. The OBC display will alternate between the two modes when the S/R button is pushed.