Maintenance Required Lamp/Indicator: Description and Operation

GF00.20-P-0004FL Active Service System (ASSYST PLUS), Function
- MODEL 212.0/ 2

Function requirements, general
- Circuit 15 ON

The electronic ignition lock control unit (N73) transmits the circuit status of circuit 15 via interior CAN (CAN B) to the instrument cluster (A1).

Active Service System PLUS (ASSYST PLUS), general
The ASSYST PLUS calculates when the vehicle is due for a service. This is true either after a precisely defined kilometer mileage or after a certain time interval, depending on which limit is reached first. In addition, it allows the driver or the service personnel an overview of the expected service operations at the vehicle.

It is calculated in the ASSYST control unit, which is integrated in the instrument cluster as a software solution. The ASSYST control unit takes into account the time and distance-dependent additional operations in accordance with the vehicle equipment. The service scope and the time that the inspection is due are displayed via the multifunction display (A1p13) in the instrument cluster.

ASSYST PLUS includes the following subfunctions:
- Function sequence for determining the remaining distance
- Function sequence for determining the remaining time
- Function sequence for evaluating data
- Function sequence for service display
- Function sequence for service interval reset

Function sequence for determining the remaining distance
While the remaining distance is calculated, the wheel speed determined by the left front axle rpm sensor (L6/1), right front axle rpm sensor (L6/2), left rear axle rpm sensor (L6/3) and right rear axle rpm sensor (L6/4) is read in by the Electronic Stability Program control unit (N30/4) (without code (233) DISTRONIC PLUS, except model 212.074/077/274/277) or Premium Electronic Stability Program control unit (N30/7) (with code (233) DISTRONIC PLUS or model 212.074/077/274/277) and transmitted to the instrument cluster over the chassis CAN (CAN E). The instrument cluster uses the received values to calculate the travel distance covered and processes this in the ASSYST control unit.
The remaining distance to the next service is determined by the countercheck with the travel distance reading that was reset and stored at the last service.
The remaining distance is the primary decisive factor for the service indicator if the remaining distance is reached before the remaining time.

The maintenance interval based on remaining distance is permanently stored in the ASSYST control unit and is 25,000 km for "Service A" or 50,000 km for "Service B".

Function sequence for determining the remaining time
The remaining time is determined in the ASSYST control unit. The remaining distance to the next service is determined by the countercheck with the time of inspection reading reset and stored at the last service.
The remaining time is the primary decisive factor for the service indicator if the remaining time is reached before the remaining distance.

The maintenance interval based on the remaining time is permanently stored in the ASSYST control unit and is 12 months for "Service A" and 24 months for "Service B".

Function sequence, evaluation of data
Apart from the evaluation factors which depend on the real driving conditions, quality factors for determining the service scope and intervals are taken into account by ASSYST PLUS. The ME-SFI [ME] control unit (N3/10) (with gasoline engine) or CDI control unit (N3/9) (with diesel engine) transmits the following variables via chassis CAN:
- Engine speed
- Engine oil pressure
- Engine oil level
- Engine torque
- Engine temperature
- Engine off time

Function sequence for service display
The following notes with service code can be shown in the multifunction display:
- Service XX in XX days
- Service XX in XXXX km/miles
- Carry out service XX

If service is past due, the following messages are shown:
- Service XX has been due for XX days
- Service XX has been due for XXXX km/miles

The display of the service date is rounded to 100 km or 100 miles or 5 days. The two-digit service code provides information on the scope of the service operations to be carried out.

The service scope is shown as a service code (e.g. "A1")
The letter denotes the scope of the maintenance and the figure behind it provides the workshop with information on additional operations. This permits the workshop to provide the customer with as accurate information as possible on the estimated time and costs of the inspection due as early as when making the appointment.

Function sequence for service interval reset
By pressing the O.K. button (S110s6) in the left multifunction steering wheel button group (S110), service can be reset.

The request is read in by the steering wheel electronics (N135) and sent over the steering LIN (LIN E1) to the steering column tube module control unit (N80). The steering column tube module control unit routes the request over the chassis CAN to the instrument cluster.
The multifunction display shows the message "Next Service". If the OK button is pressed for longer than t = 3 s, "Reset of the maintenance interval" appears in the multifunction display. The service interval has been reset.

Should an exchange of the instrument cluster become necessary, the current service data must be entered manually. The following

parameters are required for this:
- Current kilometer reading/mileage reading
- Current date
- Km reading/mileage reading during last oil change (from service booklet)
- Date of the last oil change (from service booklet)