General Information

SIA II

Models: All

Production: 1986 up to 1996 (E36 and E36/7 up to 1999)

SIA II Components:




- Instrument Cluster with LCD display
- DME
- Vehicle Speed Input
- Engine Temperature Sensor

Instrument Cluster with LED display.
The Instrument Cluster is responsible for calculating the Service Interval and displaying the LED blocks used to represent time until next service.

DME
The DME control module provides the engine speed signal used in the SIA calculation.

Vehicle Speed Input
The vehicle speed input is provided directly by a reed switch in the differential (E32,E34,E31,E36), or from a processed signal sent by the Braking and Traction (ABS/ASC) control module (E38).

Engine Temperature Sensor
The engine temperature NTC sensor provides the engine temperature signal used in the SIA calculation.

Principle of Operation




The Service Interval Indicator consists of a row of LEDs and two text messages displaying:
"OIL SERVICE" or "INSPECTION". The LEDs show the length of time remaining until an Oil service or Inspection is due. The SIA II display uses 5 green LEDs, one yellow and one red LED.

The Display LEDs are only illuminated when the ignition is first switched on. The display remains for approximately eight seconds before being switched off. The countdown to a service on a new or recently serviced vehicle starts out with all green LEDs illuminated. Over a period of time and mileage, the green LEDs will be turned off one by one. When a service is due, all green LEDs will be out and the yellow LED will be illuminated along with the text message "OIL SERVICE" or "INSPECTION".

If the service is not performed the red LED will illuminate after an additional 1000 miles has accumulated.

The calculation that the instrument cluster or IKE(E38) uses to calculate service interval is based on three pieces of data:

- Engine Speed (RPM)
- Distance Traveled (miles accumulated)
- Engine Temperature

The use of Engine Temperature and RPM for the calculation allow for a more precise estimation of when a service is required by taking driving styles into account. A vehicle for example, that is driven aggressively or for short distances in stop and go traffic may require servicing more often than a vehicle that is driven longer distances on freeways.