Engine Timing Start-Stop Function - GF07.10-P-1041MML

Engine 157.9, 276.8, 278.9 in model 217, 222 (except 222.163/173) 

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

The " Engine management, start/stop function" subfunction is examined from the point of view of the engine management.

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

• Circuit 15 (ignition ON)
• Circuit 87 M (engine management ON)
• Engine runs
• Outside temperature in range: -10°C to 40°C
• System diagnosis complete and fault-free
• Speed of 8 km/h exceeded once during forward travel

Engine management 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.

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 (N3/10) permanently performs a system diagnosis 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 (N127) and via drive train CAN (CAN C1) 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 (A1).

Engine management Start-Stop function, function sequence 

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 of ECO start/stop function button (A40/9s9) (with code 448 (Touchpad)) lights up (system is fault-free and ECO start/stop function is activated).
• Indicator lamp of ECO start/stop function button (N72s9) (with code 446 (Touchpad only)) lights up (system is fault-free and 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 not operated
• Service brake actuated up to standstill of the vehicle
• Adequate vacuum in the brake booster
• No control intervention functions from the brake and driver assistance systems
• No previous maximum full-stop braking
• Engine hood closed
• No crash signal
• Steering angle rate of change in specified value range
• Condition of the on-board electrical system OK
• Driver door closed
• Driver seat belt applied
• Interior temperature regulated
• No previous maximum full-stop braking

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

• Coolant temperature sensor (B11/4)
• Accelerator pedal sensor (B37), accelerator pedal actuation
• Crankshaft Hall sensor (B70), engine rpm
• Instrument cluster, vehicle speed via drive train CAN, powertrain control unit, suspension FlexRay, electronic ignition lock control unit (N73) and user interface CAN
• Lower control panel (N72) (with code 446 (Touchpad only)) via LCP LIN (LIN A3), touchpad (A105) (with code 446 (Touchpad only)), telematics CAN (CAN A), head unit (A26/17), user interface CAN (CAN HMI), electronic ignition lock control unit, suspension FlexRay (Flex E), powertrain control unit, and via drive train CAN:
  • ECO start/stop function status button
• Audio/COMAND control panel (A40/9) (with code 448 (Touchpad)) via telematics CAN, COMAND controller unit (A40/3) (up to model year 2018) or head unit (as of model year 2018), user interface CAN, electronic ignition lock control unit, suspension FlexRay, powertrain control unit, and via drive train CAN:
  • ECO start/stop function status button
• 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
  • Contact switch signal at the front left
  • 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
• Active Body Control, control unit (N51/2) (for code 487 Active Body Control (ABC))) via chassis FlexRay, powertrain control unit and drive train CAN:
  • Engine stop prohibition
  • Engine start request
• Radar sensors control unit (N62/1) (with code P20 (Driving Assistance package Plus)) (up to model year 2018), engine torque request (increase or reduction) via suspension FlexRay, powertrain control unit and drive train CAN
• Mercedes-Benz Intelligent Drive control unit (N62/4) (as of model year 2018), engine torque request (increase or reduction) via suspension FlexRay, powertrain control unit and drive train CAN
• Steering column tube module control unit (N80), steering wheel angle and steering wheel angular velocity via chassis FlexRay, powertrain control unit and drive train CAN
• Electronic ignition lock control unit (N73), status of ECO start/stop function button
• 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 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 be restarted using the transmitter key or over the start-stop-button 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".

The fuel system control unit receives the CAN signal "Fuel specified pressure" from the ME-SFI [ME] control unit via the drive train CAN and actuates the fuel pump (M3) with a pulse width modulated signal accordingly.

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 at brake booster not in specified range
• Brake assistance and distance control system in control intervention function
• The vacuum in the brake booster is not adequate
• 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 of one of the following systems or assembly parts: driver presence, steering, on-board electrical system, brake system, accelerator pedal, transmission, starter, 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 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.

	Electrical function schematic for engine management, start/stop		PE07.10-P-2722-97SED
	Overview of system components for gasoline injection and ignition system with direct injection	Engine 276.8 in model 217, 222 (except 222.163/173)	GF07.70-P-9998MMT
		Engine 157.9, 278.9 in model 222	GF07.70-P-9998MML