ECO Start/Stop Function Energy Management, Function - GF54.10-D-1040TSA

Model 907 

with code MJ8 (ECO start/stop function) 

Function requirements, general 

• System diagnosis completed without errors
• Outside temperature 0 to 40 °C
• Temperature of on-board electrical system battery (G1) 0 to 60 °C
• On-board electrical system battery (G1) and front passenger seat base auxiliary battery (G1/21) or engine compartment auxiliary battery (G1/24) are sufficiently charged.

Energy management for ECO start/stop function in general 

Switching off the engine when the vehicle is at a standstill reduces the fuel consumption and therefore the exhaust gas emissions. The master control unit of the ECO start/stop function is the CDI control unit or the ME-SFI control unit, which 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 subfunctions:

• Function sequence for engine stop 
• Function sequence for engine start 
• Function sequence for forced engine start 

The subfunction "Energy management for ECO start/stop function" is considered from an energy management viewpoint. Detailed information on the function of "engine management for ECO start/stop function" is available in the function description "Common rail diesel injection (CDI), function" (for diesel engine).

Function sequence for engine stop 

Additional function requirements for engine stop: 

• Stop enable issued by CDI control unit or ME-SFI [ME] control unit As the master control unit for the ECO start/stop function, the CDI control unit or the ME-SFI [ME] control unit checks the 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 SAM control unit (N10) reads in the data of the battery sensor (B95) via the battery sensor LIN (LIN B15), evaluates the data and sends information that describes the state of the on-board electrical system or the requirements on the on-board electrical system via the interior CAN (CAN B), the electronic ignition lock (EZS) control unit (N73), the suspension FlexRay (Flex E), the powertrain control unit (N127) and the powertrain CAN (CAN C) to the CDI control unit or the ME-SFI control unit.

The CDI control unit or the ME-SFI [ME] control unit evaluates all the relevant data, issues the stop enable and switches the engine off. The CDI control unit or the ME-SFI control unit then sends the signal "Drivetrain operational" back to the 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 setting is reduced. In high ambient temperatures the system changes into air circulation mode depending on the specified temperature adjusted.

Function sequence for engine start 

As soon as the driver removes his/her foot from the brake pedal, the engine starts.

By using a backup battery, the voltage drop experienced by the vehicle occupants when the engine is started (e.g. during radio or ventilation operation) is not perceived.

The CDI control unit or the ME-SFI [ME] control unit evaluates all relevant variables and starts the engine. As soon as the CDI control unit or the ME-SFI control unit detects an engine speed of 400 to 700 RPM, it terminates the starting procedure and sends the signal "Engine running" to the SAM control unit.

Function sequence for forced engine start 

To ensure that the on-board electrical system stability is also given during engine OFF, the CDI control unit or the ME-SFI [ME] control unit can also force the engine to start. A forced engine start is also conducted if, as a consequence of load-intensive consumers, the on-board electrical system stability can no longer be assured.

Load-intensive consumers can be requested e.g. by the following systems:

• Air conditioning
• Steering
• Sound system
• Comfort heater

As soon as the energy management is no longer able to ensure the stability of the on-board electrical system, the SAM control unit sends the "Start engine" request to the CDI control unit or the ME-SFI control unit. The CDI control unit or the ME-SFI [ME] 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 deactivated.

On the basis of the data of the battery sensor, the SAM control unit calculates the required specified alternator voltage and transmits this to the CDI control unit or the ME-SFI control unit. 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 control unit communicate with each other via the powertrain LIN (LIN C1). In addition, the CDI control unit or the ME-SFI control unit sends information about the operating rate of the alternator to the SAM control unit.

Detailed information about the alternator regulation can be found in the separate subfunction "Engine ON energy management function".

Electrical function schematic for energy management, ECO start/stop function	Model 907 with engine 642, 651	PE54.10-D-2075-97TSA
	Model 907 with engine 274	PE54.10-D-2075-97TSB