Vehicle Maintenance and Condition Monitoring System (ASSYST) (Mercedes-Benz Vito W639)

This system monitors the timeliness of vehicle maintenance both in terms of time intervals and the distance traveled between maintenance visits, depending on the vehicle operating conditions.

In addition, the system can monitor the condition of the oil in the engine.

ASSYST system functions

Function for determining the remaining mileage before maintenance

The vehicle mileage between maintenance services is divided into two distances:

• initial run;
• mileage remaining until the next maintenance.

Initial mileage is the minimum distance a car can travel before the next maintenance. Initial mileage depends on the following factors.

• The amount of oil added during replacement.
• Generalized qualitative factors (driving style, operating conditions in a given country). These factors are pre-installed in the system at the manufacturer and can be changed using the STAR DIAGNOSIS diagnostic system. These indicators do not depend on specific conditions (eg driving style).

Remaining mileage before maintenance

Immediately after changing the oil, the remaining mileage is equal to the initial one, if the nominal amount of oil was added during the oil change. The remaining mileage is calculated from the current odometer reading to the reading that should be at the next maintenance.

The permissible mileage between maintenance services is equal to the remaining mileage, which is indicated immediately after the oil change. The maximum possible mileage should not exceed the initial mileage by more than twice (undesirable but acceptable mileage reserve).



The remaining mileage depends on a number of factors.

• Initial run.
• Real driving conditions (number of cold starts, number of engine overspeeds, number of short-distance trips, number of trips with trailer towing).

The sources of information for the ASSYST system are the following systems and devices.

• CDI control unit (N3/9 or N3/10, N3/20, N3/26, depending on the engine model) provides information about engine operating modes.
• The ESP system provides information about the speed limit and the mileage (ABS sensors).
• The oil condition sensor (B40) provides comprehensive information on the quantity, temperature and degree of contamination of the oil with oxidation products and wear of the mechanism.
• Coolant temperature sensor, allowing you to specify engine operating modes.

ASSYST system block diagram

Function for determining the time remaining until maintenance

For cars with low mileage during the year, the ASSYST system can determine not the mileage, but the time remaining until the next maintenance.

The time is counted from the moment the oil is changed. The initial time is determined similarly to the initial run and is taken to be equal to 730 days.

The remaining time at the start of the countdown is equal to the initial time.

The maximum remaining time ranges from one to two years.

Oil level and quality indicator

The figures show the indicator of a 2006 model car (equipment code JK3, speedometer with upper divisions of the scale in km/h).