ECO Start/Stop Function Engine Management, Function - GF07.10-S-1042TRJ

Engine 274 in model 447.6/7 

with code MJ8 (ECO start/stop function) 

with code XM0 (Facelift) 

The ECO start/stop function is subdivided into the engine-side and the onboard network side scope.

The "ECO start/stop function engine management" partial function is seen from the point of view of the engine management.

Information on subfunction "Functionality of energy management ECO start/stop function" is documented in the function description "Energy management ECO start/stop function".

Function requirements for engine management, ECO start/stop function, general 

• Engine running.
• No overvoltage or undervoltage
• Outside temperature in the range from -10 to 40°C
• Speed of 8 km/h exceeded once during forward travel
• Engine hood closed
• System diagnosis complete and fault-free
• No Crash event occurred in the driving cycle

The instrument cluster control unit (IC) (A1/1) receives the information "engine running" from the ME-SFI [ME] control unit (N3/34).

Engine management, ECO start/stop function, general 

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. The fuel consumption and thus the exhaust emissions are reduced by cutting out the engine with the vehicle at a standstill.

It is still possible to stop and start the engine on request by the driver in the conventional way.

The signal acquisition and actuation module control unit (SAM) (N10/1) checks the function of all involved components and transmits the status to the ME-SFI [ME] control unit. If the function requirements are fulfilled, the driver is notified of the ECO start/stop function readiness by the "ECO" symbol in the instrument cluster.

For the ECO start/stop function, the ME-SFI [ME] control unit controls on the basis of the following sensors and signals:

• Coolant temperature sensor (B11/21)
• Accelerator pedal module (B37/4)
• Fuel pressure and temperature sensor (B4/21)
• Crankshaft Hall sensor (B70/2)
• On-board electrical system battery (G1)
• Clutch pedal switch (S40/3) and clutch pedal switch (S40/6) (with manual transmission)
• Vehicle speed via the instrument cluster control unit (IC)
• Driver seat belt buckle restraint system switch (S68/1)
• Supplemental Restraint System control unit (SRS) (N2/18), crash signal and driver seat belt buckle status
• Hood switch status (S62/41)
• Signal acquisition and actuation module control unit (SAM), engine start request, engine stop enable, hood closed
• Electronic Stability Program control unit (ESP) (N30/4), ESP® status, wheel speed, engine start request, engine stop enable, braking torque
• Left front door control unit (N69/3), left front door rotary tumbler microswitch status (M14/3s1), engine stop prohibition
• ECO start/stop function button (N72/1s5) status at upper control panel control unit (UCP) (N72/1)
• Air conditioning system control and operating unit (AAC-V & AAC-H) (S98) (with code HH4 (THERMOTRONIC automatic climate control) or with code HH9 (Semiautomatically controlled air conditioning system, TEMPMATIC)), status, engine start request, engine stop enable
• Fully integrated transmission control (VGS) electric controller unit (N15/11) (Automatic transmission with code G42 (7G-TRONIC PLUS)), engaged drive range
• Fully integrated transmission control (VGS) electric controller unit (N15/15) (Automatic transmission with code G43 (9G-TRONIC)), engaged drive range
• Fuel system control unit (FSCU) (N118) (with code G42 (7G-TRONIC PLUS)), fuel pressure
• Fuel system control unit (FSCU) (N118/9) (with code G43 (9G-TRONIC)), fuel pressure

Function sequence for ECO start/stop function engine management 

The ECO start/stop function consists of the following partial functions:

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

Function sequence for automatic engine stop 

The engine is switched off by the ME-SFI control unit if all of the following function requirements are fulfilled:

• Indicator lamp on the ECO start/stop function button lights up.
• Vehicle speed 0 km/h
• Coolant temperature between 60 and 115°C
• Engine rpm in specified value range
• Transmission in neutral (with a manual transmission)
• Drive range "D" or "N" (with automatic transmission)
• Accelerator not operated
• Service brake actuated up to standstill of the vehicle
• Engine hood closed
• No crash signal
• On-board electrical system voltage in the target range.
• Driver door closed
• Driver's seat belt applied
• Interior temperature regulated

After an automatic engine stop a maximum of three automatic engine stops are permitted without exceeding the speed threshold of 8 km/h.

After the fourth engine start, the vehicle must exceed a speed of 8 km/h for the automatic engine stop to occur again.

Additional function requirements for an automatic engine start 

• Engine OFF

Function sequence for automatic engine start 

An automatic engine start is initiated if changes occur in the system conditions.

For an A/T the engine is started automatically for release of the brake or actuation of the accelerator pedal.

The circuit relay 50 starter (K40/10kM) is actuated with a ground signal. The power contact of the starter circuit 50 relay (K40/1 0kM) closes and the solenoid switch of the starter (M1) is supplied with power from circuit 30 at circuit 50.

Via the drive CAN (CAN C), the fuel system control unit (FSCU) receives a signal from the ME-SFI [ME] control unit and according actuates the fuel pump with fuel delivery module (M3/3) with a pulse width modulated signal.

More information is available about starting the engine in the function description "Start function".

Function sequence for forced engine start 

The forced engine start subfunction is available as a protection function. Here the engine is force started autonomously (without any action taken by the driver) by the ME-SFI [ME] control unit if one of the following function requirements occurs:

• On-board electrical system voltage not in the target range
• Coolant temperature > 115°C
• Air conditioning system requires engine running (e.g. windows fogged up)
• Vacuum at brake booster not in specified range (residual pressure in brake booster falls below -200 mbar)
• Driver absence detected
• Vehicle speed > 3 km/h
• Communication error of the ECO start/stop function
• Engine hood open

A maneuvering process is recognized for an engaged gear range "R" or an engaged reverse gear and the ECO start/stop function is deactivated.

If the engine is stopped it is force started and if it is running, the engine stop function is suppressed.

The ECO start/stop function is then activated again when gear range "D" is engaged and when a vehicle speed of 15 km/h is exceeded.

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