OBC Information

Written by Johan735
Document history:
# 23 Jul 2004 Upgraded page to include OBC IV


There are two different versions of the OBC used in the E32. The OBC III and the OBC IV. The OBC III was used upto 09 1987 and was then replaced by the OBC IV. The OBC III was made by VDO and the OBC IV was made by Siemens. Both versions had a couple of software upgrades. I have no idea what was changed in these software versions.

The differences between the OBCs without the visual aspects that I noticed are:

  • OBC IV has a ANK and DIST function
  • The OBC IV can display a function's output on the checkcontrol display and at the same time show another function's output on the OBC itself.
  • The OBC IV has more "secret functions"
  • The OBC IV has two fuel consumption values.

    All OBCs are interchangeable on the E32. The E34 has versions without a checkcontrol in the instrument cluster. These OBCs have their own coding plug in the back of the unit.

    The dreaded PPPP error indicates that the OBC is unable to get it's defaults from the codeplug. If you have just disconnected the battery the values will probably reload after you start the car.


    I'll try to explain all the "secret functions of both the OBC III and the OBC IV.

    To access the secret features you have to press the "1000" and the "10" buttons at the same time. The word "test" will appear. Now you can select one of the functions mentioned below by using the "10" and "1" buttons and the "s/r" button to confirm.

    The OBC III has all functions readily available. The OBC IV needs to be unlocked before you can access these functions. To unlock the OBC IV go to test 19 and enter the secret code. The secret code is not that secret. You just have to add the day and the month and you have your unlock code. So say it's September 19th then your code will be 19+9 = 28. You
    All values shown are from my car which didn't have the engine running at the time.

    Test nr.OBC III DisplayOBC III FunctionOBC IV DisplayOBC IV Function
    Test 01 Display test Display test
    Test 02 Current fuel consumption Liters/100km Current fuel consumption Liters/100km
    Test 03 Fuel consumption Liters/Hour Fuel consumption Liters/Hour
    Test 04 Average fuel consumption for last 50km l/100km Average fuel consumption for last 50km l/100km
    Test 05 Action range on fuel in tank Action range on fuel in tank
    Test 06 Measured fuel content Measured fuel content
    Test 07 Determined fuel content (dampened) Determined fuel content (dampened)
    Test 08 Current speedCurrent speed
    Test 09 Voltage at terminal 15Voltage at terminal 15
    Test 10 Software date Speedo correction
    Test 11 n/an/a OBC language setting
    Test 12 DIAG values Average speed used for ANK calcualtion
    Test 13 PORT values Expected arrival time
    Test 14 PROM values Software date
    Test 15 n/an/a DIAG values (Fault memory)
    Test 16 n/an/a PORT values (inputs & outputs)
    Test 17 n/an/a PROM values (all data for OBC)
    Test 18 n/an/a "Code" alarmhorn beeping or contious tone
    Test 19 n/an/a Lock/Unlock OBC test functions
    Test 20 n/an/a Fuel consumption correction

    You can scroll through the diag, port and prom values by using the "1000" and "100" buttons.

    When you press "100" and "1" at the same time you get the car version. In my case 7 - 0

    Also check out this excelent OBC webpage: http://home.iae.nl/users/bts/obc.htm

    If you would like to add any comments, remarks and/or corrections to this procedure, feel free to email Mike Oswald and we'll put it on our site. Share your experiences with us so others may benefit from it.