Active Service System (ASSYST) function - GF00.20-P-0003C

MODEL 463 with ENGINES 112.945, 113.962 /982, 606.964 as of 1.4.98

15.03.07

The document has been updated to this date and will no longer be subject to revision.

Fig 1: Active Service System (ASSYST) Function Diagram

Courtesy of MERCEDES-BENZ USA

General information

The "Active Service System" (ASSYST) is a system for overall vehicle maintenance appropriate to need. The service intervals are flexible and are adapted to the actual need by means of an evaluation of the driving conditions.

A subsection of ASSYST is an engine oil maintenance system appropriate to need. This means that, in addition to a pure time and distance criterion, various factors are taken into consideration in order to calculate the service intervals. These are, on the one hand, quality factors which are encoded with HHT and, on the other hand, evaluation factors which take into account driving conditions and thus actual wear.

After dropping below a warning threshold, the remaining distance (1) or remaining time (2) is displayed in the text field and the tool symbol appears in the display.

In addition, ASSYST has an engine oil incorrect quantity indicator. With oil starvation (4) or oil overfilling (3) this is indicated in the text field and the oil can symbol appears in the display.

Due to the complexity of ASSYST, the system has its own processor in the instrument cluster.

ASSYST receives the time information from the electronic clock integrated in the instrument cluster.

The other data required are received via the CAN data line from the traction systems control unit (N47) and from the injection system control unit (N3).

CAN data required for ASSYST:

4 wheel RPM signals for calculating the speed and mileage (from traction systems control unit, N47)
Coolant temperature (from injection system control unit, N3)
Engine oil temperature (from injection system control unit, N3)
Oil level (from injection system control unit, N3)
Rotational speed (from injection system control unit, N3)
Load torque (from injection system control unit, N3)
Oil correction factor (from injection system control unit, N3)

Startup time and remaining time

The startup time refers to the service interval in days immediately following the oil change .

The startup time is not dependent on the driving conditions. However, topping up the oil has no influence on the startup time. The startup time is 730 days ( 365 days).

The startup time is automatically reset to its initial value by the oil change reset following each oil change. The startup time is an internal operand, and cannot be displayed in the instrument cluster. A display of the startup time with the HHT is possible.

The remaining time is displayed in the instrument cluster under specific conditions listed below.

The remaining time is the time remaining until the next service . The remaining time is only of importance for "Low-mileage drivers". (Usually, the remaining distance is therefore displayed.)

The remaining time is dependent:

on the startup time
on the driving conditions (Evaluation of the course covered is carried out to this end.)

However, topping up the oil has no influence on the remaining time.

ASSYST also proves to meet the requirements of "low-mileage drivers" via these dependencies. Depending on the evaluation, the service interval for "low-mileage drivers" is between 1 and 2 years.

Warning threshold (in days)

With the HHT, a warning threshold of between 5 and 30 days, with an increment of one day, can be set for the remaining time. The basic adjustment is 30 days.

Display of the remaining time

The remaining time is only basically displayed when the condition:

Remaining time (in days) x 40 < remaining distance (in km) has been fulfilled and the warning threshold has been reached.

The remaining time is then displayed:

automatically, after 5 s from starter switch in position 2 or driving mode, if the warning threshold has been reached: The service symbol and the indicator "SERVICE IN... DAYS" appear for 10 s.
automatically, after 5 s from starter switch in position 2 or driving mode, if the remaining time has been exceeded : The service symbol and the indicator "EXCEEDED BY... DAYS" appear for 10 s.

After reaching the overrun of the display at -730 days, the display stays at this value! The display is given with a resolution of one day.

at the request of the driver. The display then occurs for 10 s as above.

If at the cruise control a v-limit is set, prior to the ASSYST display the v-limit display appears briefly.

If ASSYST is missing measurement values, e.g. due to the failure of a sensor, it switches over to stored substitute values. A corresponding entry is made in the diagnostic trouble code memory of the relevant control unit.

If the operating voltage fails, the data are retained. The times without operating voltage (disconnected battery) are, however, not acquired! You can however take them into consideration using the HHT.

Engine oil monitoring

Using the oil sensor, the oil level is monitored continuously, and the corresponding data are relayed to the computer by ASSYST.

Oil top-ups are automatically detected, and result in a quantity rebate, which correspondingly extends the service interval.

Oil overfills or oil starvation are indicated in the display together with the oil can symbol.

Display of the oil starvation quantity given at maximum:

On driver request

Display of warnings is given:

automatically, at the earliest 60 s after starting the engine and oil temperature greater than 60°C:
with oil overfills: The oil can symbol and the indicator "OIL LEVEL OVER MAX" appear. A brief warning tone is additionally sounded.
with oil underfills: The oil can symbol and the indicator "OIL LEVEL UNDER MIN" appear. A brief warning tone is additionally sounded.
with oil minimum: The oil can symbol and the indicator "OIL LEVEL MINIMUM" appear. A brief warning tone is additionally sounded.
automatically 13 s after ignition ON:
- if there is no oil in the engine: The oil can symbol and the display "OIL LEVEL UNDER MIN" appear. A warning signal also sounds.

The missing quantity of oil which is displayed is no longer changed during the display. A change in the oil level cannot therefore be directly observed in the display. The new oil level is only displayed after the conditions described below have been met.

Display of the oil quantity on driver's request

10 s after the starter switch has been put in position "2" the text "DISPLAY OIL LEVEL?" appears.

If during this display, the reset button of the trip odometer is pressed twice within 1 s,

with oil starvation e.g. "Top up with 1.0 L" (or "-1.0 L") appears in the display. The display does not appear until after a waiting time has passed after engine OFF.

The waiting time is dependent on the engine oil temperature.

This is

up to 20°C 30 min
as of 60°C 1 min
In the case of other temperatures, the waiting time assumes corresponding intermediate values.

Possible displays are:

"OIL LEVEL OK",
1.0 l, 1.5 l, 2 l,
"Overfill",
"OBSERVE WAITING TIME",
"DISPLAY OIL LEVEL"

In the event of an oil sensor fault (oil level/temperature/quality, B40) the oil can symbol and the message "OIL LEVEL SENSOR DEFECTIVE" appear at the earliest 30 s after the occurrence of the fault.

For the diagnosis, the injection system control unit (N3) can also be read out with the HHT. (The instrument cluster (A1) receives this sensor data via CAN from the injection system control unit (N3)).

Oil change

Following each oil change, ASSYST must be reset. On resetting, the remaining distance and the remaining time are reset. Resetting may be performed via the instrument cluster or using the HHT.

On resetting, the following data are stored:

Current kilometer reading, rounded to 100,
Total of top-up quantities in the last interval,
Remaining distance,
Remaining time,
Product of the quality factors,
in 5 data records the data for the last 5 resets.

These data can only be read out by the HHT!

If, in the event of an oil change, the prescribed oil filling capacity is not replenished, the (internal) startup distance is reduced.

Replenishment recognition

Using the HHT the last 10 replenishment quantities and the corresponding mileage reading of the current interval can be called up.
Replenishment recognition is normally indicated via the extension of the remaining distance in the instrument cluster.