Diagnosis and Repair, Coding Plug and Obc Input Information
Diagnosis and RepairFaults 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 735i the display should read
If the display should read PPPP as shown below, 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.
OBC INPUTS AND DISPLAYS
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 gong 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.
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. Calculations take place from the last time the S/R button was pushed while the OBC was in this mode.
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.
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
- timer (stopwatch function)
HR - DATE
Pushing this button repeatedly displays the time and date alternately. Leap years are not accounted for.
Changes may be made to the time display when the HR function is selected by pushing the numeric input 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 gong 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.
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.
LIMIT
This function allows the driver to be informed by a gong 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 LIMIT button followed by the S/R button.
The gong also sounds if the vehicle speed drops 3 m.p.h. 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 display.
TIMER
This function serves as a stopwatch. It is activated by pushing the TIMER and then the S/R button. A 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.