Engine timing start-stop function - GF07.10-P-1041MRA
Engine 274.9 in model 205 (except 205.047/147/247), 253 (except 253.354/954)
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 the range: -10°C > T < 40°C
- System diagnosis complete and fault-free
- Speed of 8 km/h exceeded once during forward travel
- Sport Plus mode not selected
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 (N72/5s3) (up to YoM. 2016) or the ECO start/stop function button (N72/4s9) (as of YoM. 2016) lights up (system is fault-free and the ECO start/stop function is activated).
- Vehicle speed = 0 km/h (for an A/T)
- Vehicle speed ≤ 8 km/h (for a manual transmission)
- Coolant temperature >60°C and <115°C
- Transmission oil temperature > 10°C and < 120°C
- Engine rpm in specified value range
- Transmission in neutral (for a manual transmission)
- Gear range "D" or "N" (for a automatic transmission)
- Accelerator pedal not operated
- Service brake actuated (for a manual transmission)
- Service brake actuated until vehicle is at standstill (with automatic transmission)
- Adequate vacuum in the brake booster
- Engine hood closed
- No crash signal
- 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
The ME-SFI [ME] control unit reads in the following sensors and signals to fulfill the function requirements:
- Coolant temperature sensor (B11/4)
- Accelerator pedal sensor (B37), accelerator pedal actuation
- Crankshaft Hall sensor (B70), engine rpm
- Clutch pedal sensor (B53/1), clutch operation (for manual transmission)
- Manual transmission main shifter shaft position sensor (B79/3) (with manual transmission)
- Instrument cluster, vehicle speed via drive train CAN, powertrain control unit, suspension FlexRay (Flex E), electronic ignition lock control unit (N73) and 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, chassis FlexRay, electronic ignition lock control unit and user interface CAN:
- Indirect crash signal
- Status of driver seat belt
- Engine hood signal closed (for code U60 (Active engine hood (pedestrian protection)))
- Climate control unit (N22/1), A/C status via the interior CAN (CAN B), electronic ignition lock control unit, chassis FlexRay, powertrain control unit and drive train CAN:
- Engine stop prohibition
- Engine start request
- Contact switch signal at the front left
- Status of ECO start/stop function button on right lower control panel (N72/5), via the LCP LIN (LIN A3), over the Audio/COMAND control panel (A40/9), telematics CAN (CAN A), head unit (A26/17), user interface CAN, electronic ignition lock control unit, chassis FlexRay, powertrain control unit and via the drive train CAN to the ME-SFI [ME] control unit (up to YoM. 2016)
- Status of ECO start/stop function button on LCP left (N72/4), via LCP LIN, Audio/COMAND control panel, telematics CAN, head unit, user interface CAN, electronic ignition lock control unit, suspension FlexRay, powertrain control unit and via the drive train CAN to ME-SFI [ME] control unit (as of YoM. 2016)
- Signal that engine hood is closed, anti-theft alarm system (for code 551 (Anti-theft alarm system))
- Electronic Stability Program control unit (N30/4) via suspension FlexRay, powertrain control unit and drive train CAN:
- Brake vacuum sensor (B64/1)
- Brake actuation
- Wheel speed
- Engine start request
- Engine stop release
- Engine stop prohibition
- AIRmatic control unit (N51/3) (for code 483 (ADVANCED AGILITY package) and code 489 (AIRMATIC)) (model 205) or AIR BODY CONTROL unit (N51/3) (for code 489 (AIR BODY CONTROL)) (model 253) via suspension FlexRay, powertrain control unit and drive train CAN:
- Engine stop prohibition
- Engine start request
- Radar sensors control unit (N62/1) (with code 23P (Driver Assistance Package), engine torque request (increase or decrease) 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 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) (for A/T), status of gear range via drive train CAN
After an automatic engine stop a maximum of three automatic 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 (for code 889 (Keyless-Go).
Function sequence for automatic engine start
With a manual transmission, the engine is automatically started upon actuating the acceleration or clutch pedal. For an A/T the engine is automatically started upon releasing the brake or actuating the accelerator pedal.
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.
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 status required
- 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 on the brake booster not in the nominal range (residual pressure in the brake booster does not fall below -200 mbar)
- 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 upon recognition of rolling backwards (for an automatic transmission)
- Vehicle speed >8 km/h for forward travel and for reverse travel (for a manual transmission)
- System or communication error of the following systems: driver presence, steering, on-board electrical system, brake and control systems, accelerator pedal, transmission, starter, engine
A maneuvering process is recognized for an engaged reverse gear 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 forward gear and for exceeding a vehicle speed 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.
When Sport Plus mode is activated via the AGILITY SELECT switch (N72/4s1) (for an automatic transmission) or the AGILITY SELECT switch (N72/5s7) (for a manual transmission), the ECO start/stop function is deactivated.
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