Eco Start/Stop Function Engine Management, Function - GF07.10-P-1042MMV

Engine 276.8 in model 205, 253 

The ECO start/stop function is subdivided into the engine-side and the on-board network side scope. The "ECO start/stop function engine management" partial function is seen from the point of view of the engine management.

Function requirements ECO start/stop function, general points 

• Circuit 15 (ignition ON)
• Circuit 87 M (engine management ON)
• Engine runs
• Outside temperature in a range of: -10 to 40°C
• System diagnosis complete and fault-free
• Speed of 8 km/h exceeded once during forward travel
• Sport Plus mode not selected

ECO start/stop function, general points 

Through actuation of the ECO start/stop function button (N72/4s9) (for model 253) or (N72/5s3) (for model 205) the ECO start/stop function. To do this a request is sent by the LCP left (N72/4) (for model 253) or LCP right (N72/5) (for model 205) via LCP-LIN (LIN A3), Audio/COMAND control panel (A40/9), telematics CAN (CAN A), head unit (A26/17), user interface-CAN (CAN HMI), electronic ignition lock control unit (N73), chassis FlexRay (Flex E), powertrain control unit (N127) and drive train CAN (CAN C1) to the ME-SFI [ME] control unit (N3/10).

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.

Conventional cutting out and starting of the engine with the transmitter key (A8/1) or via the KEYLESS-GO start/stop button (S2/3) (with code 889 (Keyless-Go) continues to be possible.

The ME-SFI [ME] control unit permanently performs an SD and assesses the system conditions for the ECO start/stop function.

All of the systems participating in the ECO start/stop function constantly check their status and send this to the powertrain control unit and via drive train CAN to the ME-SFI [ME] control unit.

If the function requirements are fulfilled, the driver is notified of ECO start/stop function readiness by the "ECO" symbol in the multifunction display (A1p13) in IC (A1).

Function sequence for ECO start/stop function 

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 (a start dictated by the system) 

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 for the ECO start/stop function button lights up (system is fault-free and the ECO start-stop function is activated)
• Vehicle speed = 0 km/h
• Coolant temperature between 60°C and 115°C
• Transmission oil temperature between 10°C and 120°C
• Engine RPM in specified value range
• Gear range "D" or "N"
• Accelerator pedal not operated
• Service brake actuated up to standstill of the vehicle
• Adequate vacuum in the brake booster
• Engine hood closed
• Steering wheel angular velocity in the specified value range
• Condition of the on-board electrical system OK
• Driver door closed
• Driver seat belt applied
• Interior temperature regulated
• No control intervention functions by the suspension, brake assistance and distance control systems
• No crash signal
• No previous maximum full-stop braking
• No function-relevant faults stored

The ME-SFI [ME] control unit reads in the following sensors and signals to fulfill the function requirements:

• Coolant temperature sensor (B11/4), coolant temperature
• Accelerator pedal sensor (B37), accelerator pedal actuation
• Crankshaft Hall sensor (B70), engine RPM
• IC, vehicle speed via the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and the user interface CAN (CAN HMI)
• Supplemental restraint system control unit (N2/10), direct crash signal
• Supplemental restraint system control unit via drive train CAN, powertrain control unit, suspension FlexRay:
  • Indirect crash signal
  • Status of driver seat belt
  • Engine hood signal closed (for code U60 (Active engine hood (pedestrian protection)))
• Front SAM control unit (N10/6):
  • A/C status
  • Engine stop prohibition
  • Engine start request
  • Status of left front door open/closed
  • ECO start/stop function status button
  • Signal engine hood closed (with code (551) Anti-theft alarm system (ATA [EDW]))
• Electronic Stability Program control unit (N30/4) via suspension FlexRay, powertrain control unit and drive train CAN:
  • Brake actuation
  • Wheel speed
  • Engine start request
  • Engine stop release
  • Engine stop prohibition
  • Vacuum in brake booster
• AIRMATIC control unit (N51/3) (for model 205 with CODE 483 (ADVANCED AGILITY package) and CODE 489 (AIRMATIC)) via chassis FlexRay:
  • Engine stop prohibition
  • Engine start request
• AIR BODY CONTROL control unit (N51/3) (for model 253 with CODE 489 (AIR BODY CONTROL)) via chassis FlexRay:
  • Engine stop prohibition
  • Engine start request
• Radar sensors control unit (N62/1) (with CODE 23P (Driving assistance package plus)), engine torque request (increase or reduce) via chassis FlexRay, powertrain control unit and drive train CAN
• Left front door control unit (N69/1) status of front door left via interior CAN, electronic ignition lock control unit, chassis FlexRay, powertrain control unit and drive train CAN
• Steering column tube module control unit (N80), steering wheel angle and steering wheel angular velocity via suspension FlexRay, powertrain control unit and drive train CAN
• FSCU (N118), fuel pressure via the drive train CAN
• Fully integrated transmission control unit (Y3/8n4), status of gear range via drive train CAN

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.

Upon opening of the engine hood in automatic engine stop, the ECO start/stop function is switched off and all indicator lamps in the IC light up.

The engine must be restarted using the transmitter key or over the start/stop button KEYLESS-GO (for code 889 (Keyless-Go).

Function sequence for automatic engine start 

The engine is automatically started upon actuating the accelerator pedal or releasing the brake.

The ME-SFI [ME] control unit actuates the circuit 50 starter relay (K40/8kH) with a ground signal. The power contact on the relay closes and the starter solenoid switch (M1) is supplied at "circuit 50" with a voltage from "circuit 30".

Via the drive train CAN, the fuel system control unit receives the CAN signal "Fuel specified pressure" from the ME-SFI [ME] control unit and actuates the fuel pump (M3) accordingly by means of three phase-offset AC voltage signals.

Function sequence for forced engine start (a start dictated by the system) 

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 network condition requires the engine to run.
• Coolant temperature > 115°C
• Exceeding of the engine stop period of a maximum of 3 minutes
• A/C required engine running (e.B. windshield fogged up)
• Vacuum in brake booster not in the specified range (residual pressure in brake booster falls below -200 mbar)
• Brake assistance and distance control system in control intervention function
• Driver presence recognition (driver seat belt or driver door is opened)
• Change of the steering wheel angle by more than 8°
• Vehicle speed >2 km/h for forward travel and immediately for recognition of rolling backwards
• System or communication error from one of the following systems or components: driver presence, steering, on-board electrical system, brake system, accelerator pedal, transmission, starter (M1), engine

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

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

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. The engine is also started if the driver door is opened, the driver seat belt buckle is opened or the ECO start/stop function is switched off via the ECO start/stop function button.

Upon activation of the Sport Plus mode, the ECO start/stop function is deactivated.

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