BMW E31 UNLOCKING THE ON-BOARD-COMPUTER

OBC 'Hidden' information:

The OBC can display information that is usually hidden from the driver, this information can be very useful. For instance, the real speed of the car can be displayed (always in KPH) rather than the exaggerated speed as shown by the speedo. This is great for situations where you are in the rapidly expanding 'average speed camera areas'. In a 50MPH area you can watch the OBC and accelerate until the OBC shows 80KPH (50MPH), hit the cruise and you will notice the speedo showing 54MPH (as it over-reads by 7%) and the fact that you are edging past other traffic!

Before this hidden information can be seen, the OBC must be unlocked. This is quite simple. Turn the ignition key to position I and then press the 1000 and 10 buttons at the same time. The OBC will now show 'Test No --', use the 10 and 1 key to select Test 19, this is the unlock selection, now press the 'set/reset' button. The OBC now expects you to enter the 'unlock code'. The code is a two-digit number that is the addition of the day and the date as shown on the OBC. So, press the 'Date' button, lets say that the date is shown as '10:23', just add 10 to 23 giving 33.....and that is the unlock code! Use the 1 and 10 keys to enter 33 and the OBC is now unlocked.


Below is a list of the 'hidden' functions of the OBC.

To select a particular test press '1000' and '10' simultaneously and the OBC will show 'Test No --'. You can now select the tests shown below by using the '1' key to enter units and the '10' key to enter 10's of units.....then press the S/R key and the selected test will be displayed. Be warned that test 21 will reset all OBC data and that includes the MPG correction factor (which is usually set to default values anyway), it will also lock the OBC again:


Function Display Display Type Explanation Manipulation

1 This switches on all the LCD pixels, useful for checking if any has faded

2 0.0 V BR Varying Instantaneous fuel consumption in l/100km Measurement

3 0.0 L/H Varying Instantaneous fuel consumption in l/hr Measurement

4 14.0 TVBR Varying Average fuel consumption (used to calc. Range) Calculation from Measurements

5 135 RW Varying Current Range Calculation from Measurements

6 40 T:ADC Varying Amps Measurement

7 35 T:MTL Varying Fuel in tank as a % of full. Measurement

8 70.7 V Varying Instantaneous speed Measurement in KPH

9 14.20 uB Varying System voltage at terminal R (where ever that is) Measurement

10 0.97 EICH Setting
Steady ? Speedo meter correction *1 1000/100/10/1 button to change, S/R to save
This doesn't work on my car

11
LA-J
LA-CAN
LA-F
LA-E
LA-I
LA-CH
LA-UK
LA-D
LA-US
LA-FCH Setting Country Setting for language, miles/km, C/F and "l/100Km"/"Km/l" 1000/100 button to change, S/R to save

12 62.9 VANK Varying Average Speed for calc. ETA Calculation from Measurements

13 23.40 ZANK Varying ETA, Estimated time of arrival, provided the required distance is entered ? Calculation from Measurements

14 06.05.1987 89 735I *4
04.04.1990 92 740IA*4
Steady Software Date of OBC NONE

15 92 740IA*4 89 750ILA*4
DIAG Values Values
01 01 C1
02 52 52
03 C3 C3
04 04 A4
05 05 C5
06 06 C6
07 07 E7
08 00 20
09 00 02
Fixed Setting Diagnostic OBC values 1000/100 to up/down DIAG number, no manipulation, no save

16 92 740IA*4 89 750ILA*4 89 735I*4
PORT Values Values Values
01 80/83/87 A0 C1
02 40 05 52
03 1E/5E 00 C3
04 16 1F 0C
05 02/06 46 C5
06 40 D0 C6
07 80 A8 A7
08 04/40/44 7F 70
09 0F 00 00
Varying OBC input port values, depending on engine running or not, etc. 1000/100 to up/down PORT, no save *3

17 92 740IA*4 89 750ILA*4 89 735I*4
PROM Values Values Values
00 D1 9F 64
01 00 00 00
02 00 00 00
03 00 00 00
04 64 64 CA
05 78 64 6E
06 50 42 4C
07 28 24 2D
08 0E 0F 10
09 0C 0E 0F
0A 89 6E C8
0B C7 DE DD
0C DE F1 EE
0D E9 F6 FC
0E 00 01 05
0F 53 61 14
10 C6 C6 CB
11 36 6A 58
12 00 00 00
13 00 00 00
Fixed Setting Vehicle Specific Data, changing between car models NONE

18 HUPEITION
HUPEDTION Setting Horn/Claxon, either single tone or double tone C/F to select, S/R to save

19 LOCK
FREI Setting UNLOCK/LOCK OBC functions,
Add current day and month (as known to OBC) and enter this value 10/1 to set unlock value and S/R to unlock, C/F to lock

NOTE: For instance, if the date was 12th of November, add 12 (the day) to 11 (the month) giving a value of 23; enter this into the OBC using the '1' and '10' keys and then press 'S/R' to unlock, if you need to lock the OBC then press 'C/R' instead.

20 A strange test that turns all pixels off, pressing any key light a square of pixels above or below the key


21 The display gets very bright and then reverts to 'locked' mode