A Typical 3 series Instrument Cluster
and "inspection" service lights were put in place in 1982
to help owners remember when to return to a service center for routine
maintenance, such as oil changes and general inspection of all hoses,
belts, etc.... It's actually a great idea- one that has really caught
on ( Mercedes, Volvo and others are following BMWs lead)
Causes the SII (service interval indicator) lights to come on?
The SII lights
are not "event" triggered. What that means is that they
are not reporting a component failure or warning of imminent failure.
Rather, the SII light computer "estimates" miles traveled.
Once it estimates you have gone a certain number of miles it illuminates
one of the SII lights (i.e. Oilservice- 7,500 estimated miles, or
Inspection-15,000 estimated miles*). Mileage is estimated based
on a formula:
details of the service reminder lights:
Mileage is estimated
based on the following formula:
if engine temperature is below operating temperature, else t=0
if engine is above 4500 RPM, else r=0
you traveled 5 miles with a cold engine running at 5000 RPM, the
SII computer would actually "estimate" 12.5 miles traveled:
(the actual miles traveled)
(because the engine was cold)
(the engine was exceeding 4500 RPM)
X (1+1+.5)=12.5 estimated miles (from
a trip of only 5 miles)
Once the computer reaches a certain count value (about 7,500 miles
for Oilservice and 15,000 miles for inspection*), it will illuminate
one of the service lights (oilservice or inspection) seen below.
The five green
"countdown" lights are there to let you know approximately
how long it will be before the next time your Oilservice or Inspection
light will come on.
- Say an Oilservice
or Inspection is due in 3000 miles, and
- There are
three green lights remaining (they shut off within 15 seconds
of starting your engine)
So; 3000 miles
remaining divided by 3 green leds = 1000 miles per Green led.
The yellow light
along with the word Oilservice/Inspection indicates service is now
due. The red lights indicate service overdue by approximately 100
miles per light.
with year and model