ECO Start/Stop Function Energy Management, Function - GF54.10-P-1040GWM

Model 463 (except 463.342) 

as of Model year 2019 

Function requirements, general 

• Engine running and at operating temperature
• System diagnosis completed without errors
• Outside temperature -10 up to 40 °C
• On-board electrical system battery temperature (G1) 0 up to 60 °C
• On-board electrical system battery charged sufficiently

Energy management for ECO start/stop function in general 

Switching of the engine when the vehicle is at a standstill reduces the fuel consumption and therefore the carbon dioxide emissions. The master control unit for the ECO start/stop function is the powertrain control unit (N127), that records and evaluates all influencing factors.

For a stationary vehicle, the ECO start/stop function switches the engine off automatically and starts it again, as soon as the driver wishes to drive off.

It is still possible to stop and start the engine in the conventional way.

The ECO start/stop function encompasses the following sub-functions:

• Engine stop 
• Engine start 
• Forced engine start 

Additional function requirement for engine stop 

• Stop enable issued by powertrain control unit

Engine stop 

As the master control unit for the ECO start/stop function, the powertrain control unit checks various influencing factors for the stop enable. The energy management system provides information for this which describes the on-board electrical system status or the requirements for the on-board electrical system.

The front SAM control unit (N10/6) reads in the data from the battery sensor (B95) over the battery sensor LIN (LIN B15), evaluates the data and sends information describing the condition or the load requests to the 12V on-board electrical system, over the interior CAN (CAN B), electronic ignition lock control unit (N73) and the suspension FlexRay (Flex E) to the drivetrain control unit.

The powertrain control unit evaluates all the relevant data, issues the corresponding stop enable and then switches off the engine. The powertrain control unit then sends the "Drivetrain operational" signal over the chassis FlexRay, electronic ignition lock control unit and the interior CAN to the front SAM control unit. This prevents the energy management system from reducing or switching off consumers if the "Engine running" signal is not sent.

If the air conditioning system automatic mode is active, the blower output is reduced. In high ambient temperatures the system changes into air circulation mode depending on the specified temperature adjusted.

After an engine stop, a maximum of three engine starts within one minute are permitted without exceeding the speed threshold of v = 8

km/h.

Engine start 

The following events lead to an engine start:

• The brake pedal is released (when the HOLD function is not active and the transmission position is D or N).
• The accelerator pedal is operated.
• The transmission mode is changed.
• Reverse gear "R" is engaged.
• Transmission position "P" is exited.
• The vehicle moves off.
• The temperature in the vehicle interior leaves the selected range.
• The windshield is fogged (A/C system switched on).

The powertrain control unit evaluates all relevant variables and starts the engine. As soon as the powertrain control unit recognizes an engine speed of 400 to 700 RPM, it ends the start procedure and sends the "Engine running" signal over the chassis FlexRay, electronic ignition lock control unit and the interior CAN to the front SAM control unit.

Forced engine start 

To ensure that the on-board electrical system stability is also available during engine OFF, the powertrain control unit can also force the engine to start. A forced engine start is also conducted if, e.g. as a consequence of a request for load-intensive consumers, the on-board electrical system stability can no longer be assured.

The following events result in a forced engine start:

• Brake Assist or the distance control is active.
• The driver seat belt is released.
• Driver door is open.
• The ECO start/stop function is switched off.

As soon as the energy management is no longer able to assure the stability of the 12-V on-board electrical system, or if one of the above-mentioned events occurs, the front SAM control unit sends the "Start engine" request over the interior CAN, electronic ignition lock control unit and the chassis FlexRay to the powertrain control unit. The powertrain control unit then starts the engine.

If, following this, the on-board electrical system stability can still not be assured, the engine is no longer switched off. The ECO start/stop function is switched off.

The front SAM control unit uses the data from the battery sensor as a basis for calculation of the specified alternator voltage and sends this over the interior CAN, electronic ignition lock control unit, suspension FlexRay, powertrain control unit and the drive train CAN to the CDI control unit (N3/9) (diesel engine) or to the ME-SFI [ME] control unit (N3/10) (gasoline engine). This makes the CDI control unit or the ME-SFI [ME] control unit start the alternator regulation (alternator management). For this purpose, the CDI control unit or the ME-SFI control unit evaluates the operating rate of the alternator (G2) and requests the corresponding specified voltage. The alternator and the CDI control unit or the ME-SFI [ME] control unit communicate with each other via the drive train LIN (LIN C1). The CDI control unit or the ME-SFI [ME] control unit also sends information on the alternator operating rate over the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and the interior CAN to the front SAM control unit.

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