Maintenance Required Lamp/Indicator: Description and Operation

GF00.20-P-0004CE Active Service System (ASSYST PLUS), Function
MODEL 204.0 /2
- as of model year 2009
/YoM 08
MODEL 204.3
MODEL 204.9

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 (ASSYST PLUS), general
The ASSYST PLUS determines the service date either based on a precisely defined kilometer mileage or a certain time interval, depending on which limit is reached first. In addition, it enables an overview of the expected service work. The calculation is performed in the ASSYST PLUS, which is integrated into the instrument cluster as a software solution.

The ASSYST PLUS takes into account the time and distance dependent additional operations in accordance with the vehicle equipment.
The display for the scope and time of the due inspection occurs in the travel distance display (A1p7) (model 204.0/2/3/9 (except 204.077/277/377) without code (442) Comfort multifunction steering wheel) or in the multifunction display (A1p13) (with code (442) Comfort multifunction steering wheel, model 204.077/277/377) in the instrument cluster. ASSYST PLUS comprises 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
When determining the remaining distance, 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) and sent via chassis CAN (CAN E) to the instrument cluster.
The instrument cluster uses the received values to calculate the travel distance covered and processes this in ASSYST PLUS. 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 the remaining distance is permanently stored in the ASSYST PLUS and is currently 25,000 km for "Service A" or 50,000 km for "Service B" for European countries.

Function sequence for determining the remaining time
The remaining time is determined in the ASSYST PLUS. 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 PLUS 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 level
- Engine torque
- Engine temperature
- Engine off time

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

In the event that the service date is exceeded, 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 or letter behind it provides the workshop with information on additional operations. This enables the workshop to provide the customer with the most accurate information possible on the time and costs of the inspection due as early as when making the appointment.

Function sequence for service interval reset
The left multifunction steering wheel button group (S110) and right multifunction steering wheel button group (S111) can be used to reset the service.
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 forwards the request over the chassis CAN to the instrument cluster.
This is shown in the travel distance display or multifunction display.

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 km reading/mile reading
- Current date
- km reading/mile reading at the last oil change (from service booklet)
- Date of the last oil change (from service booklet)
- Calculation data of the ASSYST PLUS