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

Engine 274 in model 447, 448

with code MJ8 (ECO start/stop function) except 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 runs
No overvoltage or undervoltage
Outside temperature in a range of: -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 IC (IC) control unit (A1/1) receives the information "engine running" via the chassis CAN (CAN E) 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.

N73The signal acquisition and actuation module control unit (SAM) (/1) also checks the function of all associated components and transmits the status via the interior CAN (CAN B), the electronic ignition lock control unit (EZS) (N10) and via the chassis CAN 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 control unit (IC).

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) over direct line
Accelerator pedal module (B37/4) over direct line
Fuel pressure and temperature sensor (B4/21) over direct line
Crankshaft Hall sensor (B70/2) over direct line
Transmission neutral position sensor (B79/2) (for a manual transmission) over direct line
On-board electrical system battery over direct line
Clutch pedal switch (S40/3) and clutch pedal switch (S40/6) over direct line (for manual transmission)
Vehicle speed over IC control unit (IC) and chassis CAN
Supplemental Restraint System control unit (SRS) (N2/18), driver crash signal, status of seat belt via the chassis CAN
SAM control unit (SAM), engine start request, engine stop prohibition, engine hood closed via interior CAN, electronic ignition lock control unit (EZS) and chassis CAN
Electronic Stability Program control unit (ESP) (N30/4), status ESP®, wheel speed, engine start request, engine stop release, braking torque via chassis CAN
Left front door control unit (N69/3) status of left front door rotary tumbler microswitch (M14/3s1), engine stop prohibition via interior CAN, electronic ignition lock control unit (EZS) and via chassis CAN
Status of ECO start/stop function button (N72/1s5) on UCP control unit (UCP) (N72/1), via battery sensor LIN (LIN B15), signal acquisition and actuation module control unit (SAM), interior CAN, electronic ignition lock control unit (EZS) and via the chassis CAN
A/C control and operating unit (KLA-V & KLA-H) (S98) (with code HH4 (THERMOTRONIC automatic air conditioning)) or (with code HH9 (Semiautomatic regulated A/C, TEMPMATIC)), status, engine start request, engine stop release via the interior CAN, electronic ignition lock control unit (EZS) and via the chassis CAN
Fully integrated transmission control electric controller unit (VGS) (N15/11), engaged gear range via the drive train CAN (CAN C) (for an automatic transmission)
FSCU (FSCU) (N118), fuel pressure via the drive train CAN, also the fuel pressure signal is sent via the chassis CAN (CAN E) to the electronic ignition lock control unit (EZS)

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 [ME] 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 >60°C and <115°C
Engine rpm in specified value range
Transmission in neutral (for a manual transmission)
Gear range "D" or "N" (for a 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 in the engine stop in order to again switch into automatic engine stop.

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

The fuel system control unit (FSCU) receives a signal from the ME-SFI [ME] control unit via the drive train CAN and actuates the fuel pump with fill level sensor (M3/6) accordingly using 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
A/C required engine running (e.B. windshield fogged up)
Vacuum on the brake booster not in the nominal range (residual pressure in the brake booster does not fall 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 subsequently activated again for an engaged gear range "D" and for exceeding a vehicle speed of 15 km/h.

Electrical function schematic for engine management, ECO start/stop function	Engine 274 in model 448 with code MJ8 (ECO start/stop function) except code XM0 (Facelift)	PE07.10-S-2724-97VDC
	Engine 274 in model 447 with code MJ8 (ECO start/stop function) except code XM0 (Facelift)	PE07.10-S-2724-97TRC
Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-S-9998TRC