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From: (Peter Lehman )
Date: Sun, 1 Oct 1995 20:12:13 -0700
Subject: OBC "Secrete" Functions

Someone asked to know thre "secrete" functions available on the OBC. Here they are for OBC 3,4,and 5 as well as the E36 Multifunction clock.

E34 and E32

Other helpful functions can be called up by pressing two number input buttons simultaneously. They are not meant for the driver, but are used for testing and servicing.

  • -calling the type I.D. number with info on unit programming: buttons "1" + "100" (pressed simultaneously).
  • - switch the test mode for the input of various numbers in order to be able to call certain intermediate results and diagnosis information into the display: buttons "10" + "1000" (pressed simultaneously). The word "Test" will appear in the display. after a corresponding number, a pertinent intermediate result appears in the display while pressing SET/RES button. The following intermediate results or fixed values can be called in this manner.
    1. Activation of all elements = control of LEDs
    2. Actual consumption = value which is available at time
    3. Actual L/h consumpt. = value which is available at time
    4. RW consumpt. (averaged) = value which is available at time
    5. Range (not averaged) = value which is available at time
    6. Tank volume (not dampened) = value which is available at time
    7. Tank volume (dampened) = value which is available at time
    8. Actual speed = from speedo
    9. Operating voltage term. 15 = power supply (in volts)
    10. Date ROM (DDMMYY) = when "ROM" was described =

      manufacturing date

OBC IV E-34 and E32 Later production There are 20 test functions available on the OBC IV:

  1. matrix display activation of LEDs
  2. AVG fuel consump. (car must be moving) liters per 100/Km
  3. AVG momentary fuel consump. liters per hour
  4. Fuel consump. for range AVG last 50 Km (dampened)
  5. Fuel consump. for range determined (not dampened)
  6. Present fuel amount liters (not dampened)
  7. Present fuel amount liters (dampened)
  8. Road speed from inst. cluster K.P.H.
  9. Battery voltage Term. 15
  10. Sets reserve amount E-34 only
  11. Programming language E-34 only
  12. AVG speed for ARR time K.P.H.
  13. Arrival time undampened
  14. MFG date of ROM
  15. Fault memory for MFG purposes
  16. Check of inputs and out puts
  17. All data for OBC IV
  18. Horn sound for code alarm see note below
  19. Lock or Unlock
  20. Correction factor see note below

To activate test program press 10 and 1000 "TEST" appears in the display
Five of the test functions are unlocked (free) and will display when pressing the test number and S/R
Test 1, 10, 11, 19, and 20 are unlocked The other tests are locked and the OBC has to be unlocked to read these test functions.
To unlock OBC:
press 10 and 1000
"Test" appears in the display
press 19 and S/R
"locked" appears in the display
input the sum of the of the day and the month programmed in the

OBC. (should be today's date. example: day 30 and month 9 equal 39).
preaa S/R (OBC unlocked)

To lock OBC:
press 10 and 1000
press 19 and S/R
"free" displayed
press changeover miles/F- Km/C
OBC locked

Test function 18 changes OBC alarm horn from pulsed tone to constant tone. Use changeover button once test function is opened.

Test function 20 can adjust MPG factor to compensate for dirty fuel injectors. Range is 750 to 1250
example: MPG reading on OBC divided by actual MPG OBC reads 24 divided by actual 23 equals 1043 (ignore the decimal). I believe this function only works on E-32 750I with the OBC IV.


  1. Display test
  2. Momentary consumption (L/100Km)
  3. Momentary consumption (L/h)
  4. Range consumption (L/100Km)
  5. Momentary range (Km)
  6. Not used
  7. Fuel level from inst. cluster (L)
  8. Momentary speed (Km)
  9. Operating voltage KL-R
  10. Language change
  11. Units readout
  12. Average speed for arrival function
  13. Momentary arrival computed
  14. Data of mask
  15. Readout of fault memory
  16. I/O port status
  17. Encoding vehicle specific data
  18. Alarm mode
  19. Lock/unlock function
  20. Fuel consumption correction factor (see OBCIV)
  21. Software reset The test functions are accessed by pressing "10" and "1000" simultaneously. Test functions (1,10,18,19 and 20) are unlocked and can be called up by inputting the number and pressing "SET/RES". The other test functions are locked out. To unlock test functions select 19. "Lock on" will be displayed. Add the sum of the day and month display in the clock. Input this value followed by "SET/RES". To lock test functions call up test 19 and press "SET/RES" twice.

0. Display test

  1. Language. 5 different language displays are available. The languages are selected by scrolling with the 1 button. The language is stored with set/res.
  2. Time mode. Switches from 12 to 24 hour mode. Scroll with 1, store with set/res.
  3. Date mode. Switches from month/day to day/month. Scroll and store same as above.
  4. Temp. mode. Switches between "C" and "F" degrees. Scroll and store same as above.
  5. Quartz compensation factor display
  6. Display status shown (hex)
  7. Road speed display
  8. Display and input of "k" number To access test functions press "10" and "1000". Then the desired test number followed by set/res. The test function will cancel after several seconds or can be canceled by pressing check button.

When values are switched with the test functions they are stored in the EEPROM.

Thanks for the bandwith and I hope some of you can entertain yourselves with this.

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