RESETTING OIL SERVICE INDICATOR:
If your OBC needs to be reset after completing your oil change, there are two ways. NOTE: If you miss a step, just turn the key back off and try again:
A. Model Year 1999 to Mid-2000: You should have the older round 20-pin DLC connector under your hood behind the battery terminal, you need to use a small length of wire to connect (short) pins 7 and 19 for 3-5 seconds with the ignition key in position 1 (Accessory).
B. After Mid-2000: You should not have the 20-pin DLC connector. You only need to hold the left odometer reset button while turning the key to position 1 (Accessory). Keep holding the button for 5 or so seconds until any of the following shows in the display: OIL SERVICE or INSPECTION with RESET or RE. Release the button and press it again for another 5 or so seconds until RESET or RE flash. While the display flashes, press the button one more time briefly. If done correctly, END SIA should show up for a few seconds. All done.
Taken from: http://www.my330i.com/lof.php