Both are connected to the SI, Service Interval.
If the SI is not resetable that means the SI batteries are dead.
If the SI batteries are dead the systems can send the signal through the wrong wire and you get no signal.
SI reset and batteries
With the ignition switch at (position two) and the engine not running, grounding pin seven #7 of the diagnostic connector to pin one #1 for approximately three (3) seconds will reset the oil service lights. Grounding pin seven #7 to pin one #1 for approximately twelve (12) seconds will do an inspection service reset.
More information.
http://www.specialistcarsbmw.co.uk/stevenage/service/service_lights.htm
http://www.unofficialbmw.com/images/reset1.gif
1. Ground
4. Temperature sensor
7. Reset
8. TDC sensor yellow
9. TDC sensor shield
10.TDC sensor black
11.Start signal
12.Alternator charging excitation voltage
13.Ignition coil
14.Alternator charging supply current
15.Oxygen Heater
It will signal an oil change need between 5k and 7k depending on your indicated speed since the last reset. It will signal stealer inspections at all the predesignated miles.
http://www.eskimo.com/~dalus/bmw/e36/electrical/e36_reset_service_lights.html
SI Board Swap Out
Last but not least - the SI Board. Above is a new SI Board with lithium batteries and below is the old one. Note the blown battery on the old SI Board (green circle). The light blue rectangle shows the actual service indicator LED's which appear on your dash display. These LED's are mounted on a separate circuit board which must be pulled out of the old SI Board and plugged into the new one. This is an easy task. The purple arrow shows the orientation of the SI Board relative to the driver.
If it fails to reset then you need batteries.
Varta battery 500RST OE part.
Radio Shack: part number 23-191: $6.49 for set of two; they come w/solder tabs on them.
1.2 volts / 700mAh
Charge fully B4 installation on SI board.
Consider mounting batteries "remotely" under dash, etc. in separate holder for easy removal in future (i.e. not pulling the console out and apart); you can buy a plastic holder at RS. Run leadwires from holder to SI board connections. Makes life easy if you ever need to replace batteries again.
From Radio Shack, get:
1) You'll need a twin AA battery holder ($3)
2) 2 AA NiCAD rechargeable batteries ($6)
Later,