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

ENGINE 651.9 in MODEL 166 as of model year 2016

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.

Information for partial function "Energy management, start/stop function" is documented in the function description "Energy management function".

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

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
Speed of 15 km/h exceeded once during forward travel after a maneuvering process

Engine management start-stop function, general

With a stationary vehicle, the 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 cut out and starting of the engine with the transmitter key (A8/1) or via the Start/Stop button KEYLESS-GO (S2/3) (with code (889) Keyless-Go) continues to be possible.

The CDI control unit (N3/9) continuously performs a system diagnosis and assesses the system conditions for the ECO start/stop function.

All systems participating on the ECO start/stop function permanently check their status and transmit this via the chassis CAN 1 (CAN E1) or drive train CAN (CAN C) to the CDI 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).

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 CDI control unit if all of the following function requirements are fulfilled:

Vehicle speed = 0 km/h
Coolant temperature of ≥ 70°C at an outside temperature of -30°C to -10°C
Coolant temperature ≥ 60 °C at an outside temperature of -9 °C to 14 °C
Coolant temperature of ≥ 15 °C at an outside temperature of 15 °C to 60 °C
Coolant temperature < 110°C
Engine oil temperature of ≥ 15 °C and ≤ 120 °C
Engine rpm in specified value range
Transmission oil temperature > 10°C and < 120°C
Gear range "D" or "N"
Accelerator not operated
No previous maximum full-stop braking
Service brake actuated up to standstill of the vehicle
Atmospheric pressure > 760 mbar
Adequate vacuum (-1150 mbar to 130 mbar) in the BAS brake booster (A7/7)
Engine hood closed
No crash signal
Steering wheel angle speed within specified value range
Condition of the on-board electrical system OK
Driver door closed
Driver seat belt applied
Interior temperature regulated
Fill level in fuel tank > 2 l
Do not overload diesel particulate filter
Off-road program disabled

For the start-stop function the CDI control unit reads in the following signals:

Engine oil temperature sensor (B1)
Left fuel tank fuel fill level sensor fuel level indicator (B4/1)
Right fuel tank fuel level indicator fill level sensor (B4/2)
Coolant temperature sensor (B11/4)
Accelerator pedal sensor (B37), accelerator pedal actuation
DPF differential pressure sensor (B28/8) (with code 474 (Particulate filter))
Fuel temperature sensor (B50), fuel temperature
Crankshaft Hall sensor (B70), engine rpm
Instrument cluster (A1), vehicle speed via chassis CAN 2 (CAN E2), electronic ignition lock control unit (N73) and chassis CAN 1 (CAN E1)
Supplemental restraint system control unit (N2/10), direct crash signal
Supplemental Restraint System control unit via chassis CAN 1:
Indirect crash signal
Status of driver seat belt
SAM control unit (N10) via interior CAN (CAN B), the electronic ignition lock control unit and chassis CAN 1
Engine stop prohibition
Engine start request
Automatic air conditioning control and operating unit (N22/7) via interior CAN, electronic ignition lock control unit and chassis CAN 1:
A/C status
Engine stop prohibition
Engine start request
Electronic Stability Program control unit (N30/4) via chassis CAN 1
Wheel speed
Brake actuation
Engine stop prohibition
Engine stop release
Engine start request
AIRMATIC control unit (N51/3) via chassis CAN 1 (with CODE 489 (AIRMATIC)):
Engine stop prohibition
Engine start request
Radar sensors control unit (N62/1) (with CODE (Driving assistance package PLUS) via chassis FlexRay (Flex E), chassis gateway control unit (N93/7) (with CODE 23P Driving assistance package PLUS) and chassis CAN 1
Engine torque, increase request
Engine torque, reduction request
Left front door control unit (N69/1) via interior CAN, electronic ignition lock control unit and chassis CAN 1
Engine stop prohibition
Driver door closed
Steering column tube module control unit (N80), via chassis CAN 1
Steering wheel angle
Steering wheel angle speed
FSCU (N118), fuel pressure via the drive train CAN
Fully integrated transmission control unit (Y3/8n4), engaged gear range via drive train CAN

After an automatic engine stop a maximum of three automatic engine stops are permitted without exceeding the speed 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 (with code (889) Keyless Go).

Function sequence for automatic engine start

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

The CDI control unit actuates the circuit 50 starter relay (F58kM) by means of 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 CDI 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 CDI control unit if one of the following function requirements occurs:

On-board network condition requires the engine to run
Coolant temperature > 125°C
A/C required engine running (e.B. windshield fogged up)
Vacuum on BAS brake booster not in the nominal range (-1150 mbar up to 130 mbar)
Exceeding of the engine stop period of a maximum of 3 minutes
Driver presence recognition
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 in one the following systems: driver presence, steering, on-board electrical system, brake and management systems, accelerator pedal, transmission, starter, engine, chassis

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 seat belt buckle for the driver is unfastened or the ECO start/stop function is switched off.

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