ECO Start/Stop Function Engine Management, Function - GF07.10-P-1042MRS

Engine 264.9 in Model 205, 253 

The ECO start/stop function is subdivided into the Engine-side and the on-board network side scope.

This function is seen from the point of view of the Engine management.

Function requirements, general 

• Engine runs
• Outside temperature -10 to 40 °C
• System diagnosis complete and fault-free
• One-time exceeding of 8km/h for forward travel
• No brake assist system control intervention function

The ME-SFI [ME] control unit (N3/10) detects the Engine running via the evaluation of the crankshaft Hall sensor signals (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.

The front SAM control unit (N10/6) transmits the outside temperature via the interior CAN (CAN B), electronic ignition lock control unit (N73), suspension FlexRay (Flex E), powertrain control unit (N127) and drive CAN (CAN C1) to the ME-SFI [ME] control unit.

Engine management ECO start/stop function 

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 or the system requests Engine running. 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 in the conventional way.

The powertrain control unit permanently performs a system diagnosis and evaluates the system statuses for the ECO start/stop function.

All active systems that may be impaired by a shutoff Engine constantly check their status. As soon as the status of a system permits an Engine stop, it transmits its release to the powertrain control unit.

The operational readiness of the ECO start/stop function is shown to the driver by the "ECO" symbol in the instrument cluster (A1).

The powertrain control unit transmits the request to activate the "ECO" symbol via the suspension FlexRay, electronic ignition lock control unit and user interface CAN (CAN HMI) to the instrument cluster.

The ECO start/stop function is activated and deactivated via the ECO start/stop function button (N72/4s3) (model 205) or via the ECO start/stop function button (N72/4s9) (model 253) in the left lower control panel (N72/4). The left lower control panel directly reads in the status of the ECO start/stop function button and transmits this via the LCP-LIN (LIN A3), Audio/COMAND® control panel (A40/9) (except code 446 (Touchpad only)) or touchpad (A105) (with code 446 (Touchpad only)), Telematics CAN (CAN A), head unit (A26/17), user interface CAN, electronic ignition lock control unit and suspension FlexRay to the powertrain control unit.

The ECO start/stop function contains the following subfunctions:

• Automatic Engine stop 
• Automatic Engine start 
• Forced Engine start (start dictated by the system) 

Automatic Engine stop 

The Engine is shut off, if all the following requirements are fulfilled:

• ECO start/stop function activated
• Vehicle speed 0 km/h

  The instrument cluster transmits the vehicle speed via the user interface CAN, electronic ignition lock control unit and suspension FlexRay to the powertrain control unit.

• ECO start/stop function enable issued by ME-SFI [ME] control unit For this purpose, the ME-SFI [ME] control unit evaluates the coolant temperature (60 to 115 °C) and the Engine speed.

  The ME-SFI [ME] control unit directly reads in the signals of the coolant temperature sensor (B11/4) and crankshaft Hall sensor and transmits the enable via the Engine CAN (CAN C) to the powertrain control unit.

• Transmission oil temperature 10 to 120 °C

  The fully integrated transmission control unit (Y3/8n4) transmits the transmission oil temperature via the drive CAN to the powertrain control unit.

• Drive range "D", "N" or "P" engaged

  The fully integrated transmission control unit transmits the engaged drive range via the drive CAN to the powertrain control unit.

• Accelerator not operated

  The powertrain control unit directly reads in the signals of the accelerator pedal sensor (B37).

• ECO start/stop function enable issued by Electronic Stability Program control unit (N30/4)

  To do this, the Electronic Stability Program control unit monitors the wheel speed and direction of rotation, brake application up to a standstill, and the vacuum in the brake booster.

  The Engine is not shut off after a maximum full-stop braking. The Electronic Stability Program control unit transmits the enable via the suspension FlexRay to the powertrain control unit.

• Hood closed (except code U60 (Active hood (pedestrian protection)))

  The front SAM control unit transmits the status of the hood via the interior CAN, electronic ignition lock control unit and the suspension FlexRay to the powertrain control unit.

• Hood closed (with code U60 (Active hood (pedestrian protection)))

  The Supplemental Restraint System control unit (N2/10) transmits the status of the hood via the user interface CAN, the electronic ignition lock control unit, and the suspension FlexRay to the powertrain control unit.

• ECO start/stop function enable issued by climate control unit (N22/1)

  Once the vehicle interior temperature has been adjusted and the windshield is clear, the climate control unit transmits the enable via the interior CAN, electronic ignition lock control unit and suspension FlexRay to the powertrain control unit.

• V on-board electrical system status OK

  The front SAM control unit transmits the status of the 12 V on-board electrical system via the interior CAN, electronic ignition lock control unit and suspension FlexRay to the powertrain control unit.

• Status of 48 V on-board electrical system OK (with code B01 (48V Technology))

  The DC/DC converter control unit (N83/1) transmits the information via the interior CAN, electronic ignition lock control unit and suspension FlexRay to the powertrain control unit.

• Status of starter-alternator (M1/10) (with code B01 (48V Technology))

  The starter-alternator transmits the signals (alternator rotational speed and torque) via the hybrid CAN (CAN L) to the powertrain control unit.

The powertrain control unit transmits the enable for Engine stop via the drive CAN to the ME-SFI [ME] control unit. The ME-SFI [ME] control unit transmits the status via the drive CAN to the powertrain control unit.

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 Engine to be stopped again.

Upon opening the Engine hood in automatic Engine stop, the ECO start/stop function is switched off and all indicator symbols in the instrument cluster light up.

The Engine must then be restarted by the driver.

A warning tone is output if the Engine was shut off by the ECO start/stop function and the driver exits the vehicle. The message "Veh. is operational, switch off ignition before exiting vehicle" also appears in the instrument cluster. If the ignition is not switched off, the ignition is automatically switched off after a minute.

Automatic Engine start 

The Engine is started automatically if one of the following events occurs:

• The ECO start/stop function is deactivated via the ECO start/stop function button.
• The brake is released while the transmission is in drive range "D" or "N".

  No Engine start occurs in drive range "P" when the brake is released.

• The accelerator pedal is operated.
• The drive range is shifted from "P" to another drive range.

  No Engine start occurs in the case of a change from drive range "D" or "N" to "P".

• The transmission mode is changed.
• Drive range "R" is engaged.

The powertrain control unit evaluates the input factors, and transmits the Engine start request via the drive CAN to the ME-SFI [ME] control unit.

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

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

Forced Engine start (start dictated by the system) 

To ensure the on-board electrical system stability and the function of the safety-relevant systems, the Engine can be force started by the system.

The Engine is started if the on-board electrical system is e.g. placed under strain by load-intensive consumers or a function or stop requirement is no longer met.

If the on-board electrical system stability can subsequently still not be ensured, the ECO start/stop function is switched off and the Engine is no longer shut off.

The following events also lead to a forced Engine start:

• Engine stop period of a maximum of 3 minutes exceeded
• Detection of rolling backwards
• System or communication error of the following systems:
  • On-board electrical system
  • Brake system
  • Accelerator pedal
  • Transmission
  • Motor

	Electrical function schematic for Engine management, ECO start/stop function		PE07.10-P-2724-97FBI
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