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ECO Start/Stop Function Energy Management, Function - GF54.10-P-1040GN

MODEL 166 as of model year 2016 

with CODE B03 (ECO start/stop function) 

MODEL 292 

with CODE B03 (ECO start/stop function) 

IMPORTANT The "energy management for ECO start/stop function" subfunction is considered from the viewpoint of the energy management. Information on the subfunction "Engine management for start/stop function" is documented in the function description "Common rail diesel injection (CDI), function" (with diesel engine) or "Gasoline injection and ignition system with direct injection, function" (with gasoline engine).

Function requirements, general 

Energy management for ECO start/stop function in 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. Switching of the engine during standstill periods of the vehicle reduces the fuel consumption and therefore the carbon dioxide emissions. The master control unit for the engine start/stop function is the CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) that records and evaluates all influencing factors.

IMPORTANT The conventional switching off and starting the engine with the transmitter key (A8/1) or via the KEYLESS-GO start/stop button (S2/3) (with CODE 889 (KEYLESS-GO) or CODE 893 (KEYLESS-GO start function)) continues to be possible.

IMPORTANT Through the use of the additional battery for ECO start/stop function (G1/13) with a capacity of 12 Ah, the starting voltage dip is avoided while the engine is being started. The additional battery for ECO start/stop function then assumes the power supply for the active consumers in the process while the on-board electrical system battery is isolated from the on-board electrical system (at engine start). Active comfort functions are not switched off. Immediately after the engine's cold start, the ME-SFI [ME] control unit performs a system diagnosis and evaluates the functional capability of the ECO start/stop function. In addition the SAM control unit (N10) checks the function of the components involved in isolating the on-board electrical system battery and connecting the ECO start/stop function additional battery.

IMPORTANT The additional battery for the ECO start/stop function is activated by actuation of the ECO start/stop function additional battery relay (K114). The on-board electrical system battery is disconnected from the on-board electrical system by actuating the decoupling relay (F32/3k1) in the engine compartment prefuse box (F32/3). In addition, the SAM control unit (N10) checks the function of the components involved in switching in the ECO start/stop function additional battery and isolating the on-board electrical system battery.

The ECO start/stop function encompasses the following subfunctions:

Additional function requirement for engine stop 

Function sequence for engine stop 

As the master control unit for the ECO start/stop function, the CDI control unit or the ME-SFI [ME] control unit checks the various influencing factors for the stop enable.

The SAM control unit reads in the data from the battery sensor (B95) via battery sensor LIN (LIN B15), evaluates it and transmits information about the on-board electrical system status or the requirements for the on-board electrical system to the CDI control unit or ME-SFI control unit via interior CAN (CAN B), electronic ignition lock control unit (N73) and chassis CAN 1 (CAN E1).

The following information is included in it:

The CDI control unit or the ME-SFI [ME] control unit evaluates all the relevant data, issues the stop enable and switches the engine off. The CDI control unit or the ME-SFI [ME] control unit then sends the signal "Drive train ready" over the chassis CAN 1, electronic ignition lock control unit and interior CAN to the SAM control unit. This prevents the on-board electrical system management from starting the process of consumer reduction or consumer shutoff as the signal "Engine running" is not transmitted.

IMPORTANT While the vehicle is at a standstill the brake pedal must remain pressed or the "Hold" function be active. The blower output is reduced when the automatic blower speed function of the air conditioning is active. In high ambient temperatures the system changes into air circulation mode depending on the specified temperature adjusted.

After an engine stop a maximum of three engine starts is permitted without exceeding the speed threshold of v = 8 km/h.

Function sequence for engine start 

The engine starts by pressing down the accelerator pedal.

Vehicles with hybrid drive (model 166.063): 

During the starting procedure the on-board electrical system battery is isolated from the on-board electrical system. Active consumers are now provided with power by the ECO start/stop function additional battery (with CODE B03 (ECO start/stop function) and CODE ME05 (HYBRID DRIVE 80KW-VARIANT (INCLUDING PLUGIN)) except CODE 4U7 (Start/stop voltage dip fuse)). This serves to prevent any voltage dip as perceived by vehicle occupants when starting the engine (e.g. during radio or ventilation operation).

The ME-SFI [ME] control unit evaluates all relevant influencing factors and then issues the start enable (hot start signal). The front SAM control unit reads in this hot-start signal via a direct line and directly actuates the ECO start/stop function additional battery relay and the decoupling relay. The ECO start/stop function additional battery (with CODE B03 (ECO start/stop function) and CODE ME05 (HYBRID DRIVE 80KW-VARIANT (INCLUDING PLUGIN)) except CODE 4U7 (Start/stop voltage dip fuse)) is switched through to the on-board electrical system. The decoupling relay isolates the on-board electrical system battery from the on-board electrical system for the duration of the starting procedure. The power requirement of the on-board electrical system is now met exclusively by the ECO start/stop function additional battery (with CODE B03 (ECO start/stop function) and CODE ME05 (HYBRID DRIVE 80KW-VARIANT (INCLUDING PLUGIN)) except CODE 4U7 (Start/stop voltage dip fuse)). The on-board electrical system battery now supplies the energy required for the engine starting process.

As soon as the ME-SFI [ME] control unit detects an engine speed of n = 400 to 700 rpm, it stops the starting procedure and sends the "engine running" signal via the engine CAN, powertrain control unit, chassis CAN 1, electronic ignition lock control unit, and interior CAN to the SAM control unit. The SAM control unit then directly actuates the decoupling relay and the ECO start/stop function additional battery relay.

The decoupling relay connects the on-board electrical system battery to the on-board electrical system. The ECO start/stop function additional battery relay disconnects the ECO start/stop function additional battery (with CODE B03 (ECO start/stop function) and CODE ME05 (HYBRID DRIVE 80KW-VARIANT (INCLUDING PLUGIN)) except CODE 4U7 (Start/stop voltage dip fuse)) from the on-board electrical system. The energy requirement of the on-board electrical system is now supplied again by the on-board electrical system battery.

Vehicles with conventional drive concept (except model 166.063): 

By using the voltage dip limiter (R62) (series resistor) (with CODE 4U7 (Start/stop voltage dip fuse)) at the positive terminal of the on-board electrical system battery, the noticeable voltage dip for the vehicle occupants when starting the engine (e.g. during operation of the radio or ventilation mode) is reduced.

The CDI control unit or the ME-SFI control unit evaluates all relevant variables and starts the engine. As soon as the CDI control unit or ME-SFI [ME] control unit detects an engine speed of n = 400 to 700 rpm, it stops the starting procedure and sends the "engine running" signal via the drive train CAN, chassis CAN 1, electronic ignition lock control unit, and interior CAN to the SAM control unit.

Function sequence for forced engine start 

To ensure that the on-board electrical system stability is also given during engine OFF, the CDI control unit or the ME-SFI [ME] control unit can also force the engine to start. A forced engine start is also conducted if, as a consequence of load-intensive consumers, the on-board electrical system stability can no longer be assured.

IMPORTANT Load-intensive consumers can be requested by the following systems:

IMPORTANT As part of system optimization, the engine on vehicles with hybrid drive can also be forced to start. For example when the charge level of the high-voltage battery drops below a defined limit. Detailed information can be found in the function description "Hybrid drive system function" in the subfunction "Automatic engine start function".

As soon as the on-board electrical system management is no longer able to ensure on-board electrical system stability, the SAM control unit sends a "Start engine" request via the interior CAN, electronic ignition lock control unit, and chassis CAN 1 to the CDI control unit or ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit receives this and starts the engine.

If, following this, the on-board electrical system stability can still not be assured, the engine is no longer switched off. The engine start/stop function is deactivated.

The SAM control unit calculates the required alternator specified voltage based on the data from the battery sensor and transmits this to the CDI control unit or to the ME-SFI control unit via interior CAN, electronic ignition lock control unit and chassis CAN 1. This makes the CDI control unit or the ME-SFI [ME] control unit start the alternator regulation (alternator management).

IMPORTANT Detailed information about the alternator regulation can be found in the subfunction "engine ON energy management function".

Function sequence for determining the status of the ECO start/stop function additional battery (with CODE B03 (ECO start/stop function) and CODE ME05 (HYBRID DRIVE 80KW VARIANT (INCLUDING PLUGIN)) except CODE 4U7 (Start/stop voltage dip fuse)) 

The SAM control unit runs a battery state recognition immediately after the engine is started. This provides regarding the availability of electrical power to the additional battery for the ECO start/stop function.

If the engine is switched off during the battery state recognition, the SAM control unit switches this off and discards the previous results.

In addition to battery state recognition, the voltage of the additional battery for ECO start/stop function mode in the engine start/stop function mode is measured after every engine start.

IMPORTANT The battery state recognition can be started using the diagnostic system.

The additional battery relay for the ECO start/stop function is no longer actuated under the following conditions:

In order to establish these conditions, the voltage of the ECO start/stop function additional battery is compared with an internal value. A corresponding fault message is shown in the multifunction display (A1p13) of the IC (A1). The SAM control unit sends the data required for this to the instrument cluster over the interior CAN.

Function sequence for charging the ECO start/stop function additional battery (with CODE B03 (ECO start/stop function) and CODE ME05 (HYBRID DRIVE 80KW-VARIANT (INCLUDING PLUGIN)) except CODE 4U7 (Start/stop voltage dip fuse)) 

The charging strategy of the additional battery for ECO start/stop function must take two requirements into account:

If the open circuit voltage of the additional battery for ECO start/stop function is too low (U > 12.5 V), the alternator's power limit (alternator management) is deactivated so that the additional battery for ECO start/stop function can be charged.

If the voltage dip (U < 11 V) at engine start is too large, an engine stop is deactivated for t = 5 minutes to recharge the additional battery for the ECO start/stop function.

The additional battery for ECO start/stop function is only connected when the alternator's power limit (alternator management) is not active and the on-board electrical system voltage (U > 13 V) is high enough. Cut-in of the ECO start/stop function additional battery is interrupted again if the output limitation of the alternator is active or the on-board electrical system is severely overloaded.

  Electrical function schematic for energy management for engine start/stop   PE54.10-P-2070-97NBA
  Overview of energy management system components   GF54.10-P-9990GN 
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