http://www.bmwe34.net/E34main/Upgrade/OBC.htm Quote:
Originally posted by the above link
f the OBC appears to be reporting inaccurate fuel consumption figures it can be calibrated to give the correct values. - Fill the fuel tank to the maximum and reset the trip counter and one of the OBC's average fuel consumption monitors. Run the fuel tank nearly empty and fill the fuel tank again to the maximum. The amount of fuel it now takes to fill the tank is the amount used to cover the distance recorded on the trip meter so, from this, work out the actual fuel consumption of the car and then compare this to what the OBC reported as the average fuel consumption. If these two average fuel consumption figures are not exactly the same then you need to calibrate the OBC by entering a new correction factor.
The fuel consumption correction factor is a locked function of the OBC so before you can access it, you must first unlock the OBC - Access the OBC test menu by simultaneously pressing the 1000 and 10 keys so that the display changes to "TEST". With the 10 & 1 keys enter 19 on the display and then press the S/R button. Add the current day and month (as it is known to the OBC) and enter this value and then press the S/R button, the OBC should now be unlocked. To access the fuel consumption calibration factor you once more need to simultaneously press the 1000 and 10 keys so that the display changes to "TEST". With the 10 & 1 keys enter 20 (Be careful not to enter 21 as this will reset the OBC) on the display and then press the S/R button - you should now see something like 1000 CORR, this is your current correction factor. To calculate your new correction factor use the following:
new_correction_factor = old_correction_factor * actual_mpg / obc_mpg
Enter your new correction factor into the OBC using the 1000/100/10/1 keys and then press the S/R button. If you want to relock the OBC - enter function 19 again then press the C/F button to lock. |
that link talks about a upgrade to a obc for cars without one, but those two paragraphs I quoted might be helpful.
also go to the page... at the bottom there is another link to a site that has tons of technical info about the obc for e32/e34 (they are same)
