Engine off energy management, function - GF54.10-P-1050FLM

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MODEL 212 as of model year 2014

Function requirements, general

"Engine running" or "Drive train operational" signal not set (vehicle switched off)

The CDI control unit (N3/9) (diesel engine) or the ME-SFI [ME] control unit (N3/10) (gasoline engine) sends the "Engine running" or "Drivetrain operational" signal via the chassis CAN 1 (CAN E1), the front SAM control unit with fuse and relay module (N10/1) and the interior CAN (CAN B) to the rear SAM control unit with fuse and relay module (N10/2).

Engine off energy management, general

Engine off energy management ensures the stability of the on-board electrical system and the starting capability of the engine when the vehicle is parked.

This function is integrated in the rear SAM control unit and serves to extend the service life of the on-board electrical system battery (G1). To this end, active electrical consumers may be switched off.

Engine OFF energy management encompasses the following subfunctions:

Consumer shutoff function sequence
Function sequence for no-load current management
Function sequence for remote charging/jump start

Additional function requirements for consumer shutoff

Circuit 15 ON or Circuit 15R ON
On-board electrical system emergency mode not active

The electronic ignition lock control unit (N73) transmits the circuit status of circuit 15 via the interior CAN to the rear SAM control unit.

Consumer shutoff function sequence

The rear SAM control unit actuates the consumer shutoff function under the following conditions:

On-board electrical system voltage lowered to less than U = 11.8 V
Engine Off
Change from circuit 15 ON to circuit 15R ON

Given constant shutoff conditions, one consumer will be shut off every t = 5 s in addition to the consumer reduction from the engine on energy management function.

The shutoff sequence is shown in the following table.

The list includes those consumers whose power supply is reduced or cutoff as part of the engine on energy management function (up to shutoff step 17).

Shutoff step	Shutoff stage	Power-reduced or deactivated function	Executing control unit	Maximum Current in A
1	1	Heating level 6, heat boosting (engine 271.8, 642.8, 651.9), passenger side	Automatic climate control and operating unit (N22/7)	18.5
2	2	Heating level 5, heat boosting (engine 271.8, 642.8, 651.9), driver side	Automatic climate control and operating unit (N22/7)	18.5
3	3	Heating level 4, heat boosting (engine 271.8, 642.8, 651.9), passenger side	Automatic climate control and operating unit (N22/7)	18.5
4	4	Heating level 3, heat boosting (engine 271.8, 642.8, 651.9), driver side	Automatic climate control and operating unit (N22/7)	18.5
5	5	Heating level 2, heat boosting (engine 271.8, 642.8, 651.9), passenger side	Automatic climate control and operating unit (N22/7)	18.5
6	6	Heating level 1 of PTC heater booster (R22/3) (with engine 271.8, 642.8, 651.9), driver side	Automatic climate control and operating unit (N22/7)	18.5
7	7	Seat heater level 3 (with CODE 873 (Seat heater for left and right front seats))	Rear SAM control unit with fuse and relay module (N10/2)	13.2
8	8	Seat heater level 2 (with CODE 873 (Seat heater for left and right front seats))	Rear SAM control unit with fuse and relay module (N10/2)	13.2
9	9	Wiper park heater	Front SAM control unit with fuse and relay module(N10/1)	15.0
10	10	Mirror heater	Left front door control unit (N69/1) and Right front door control unit (N69/2)	3.5
11	12	Rear window heater	Rear SAM control unit with fuse and relay module (N10/2)	30.0
12	13	Rear blower (with CODE 581 (Comfort automatic air conditioning)) P = 50 %	Automatic climate control and operating unit (N22/7)	5.5
13	14	Blower in front P = 50%	Automatic climate control and operating unit (N22/7)	16.0
14	15	Fan P = 50%	Automatic climate control and operating unit (N22/7)	31.0
15	16	Circuit 15R relay (1) (N10/2kB)	Rear SAM control unit with fuse and relay module (N10/2)	6.0
16	18	Seat heater level 1 (with CODE 873 (Seat heater for left and right front seats))	Rear SAM control unit with fuse and relay module (N10/2)	3.3
17	19	Residual heat utilization (with CODE 581 (Comfort automatic air conditioning) and except CODE 494 (USA version))	Automatic climate control and operating unit (N22/7)	8.0
17	19	Rear air conditioning (with CODE 581 (Comfort automatic air conditioning))	Automatic climate control and operating unit (N22/7)	6.0
18	20	Stationary heater (with CODE 228 (Stationary heater))	Stationary heater control unit (A6n1)	10.0
19	21	Audio system	Radio (A2) (with CODE 505 (20 NTG5 radio without navigation capability) or CODE 510 (Audio 20 incl. CD changer) or CODE 522 (Audio 20 radio) or CODE 523 (MB Audio 20 radio)) or COMAND controller unit (A40/3) (with CODE 512 (COMAND APS incl. DVD changer) or CODE 526 (COMAND with single DVD drive (without navigation)) or CODE 527 (COMAND APS with single DVD drive (with navigation)) or CODE 528 (COMAND incl. DVD changer) or CODE 531 (COMAND APS))	2.0

The consumer shutoff is not canceled even if the on-board electrical system voltage stabilizes at a value above U = 11.8 V. The switched-off consumers are switched on again only after circuit 15C has been switched in.

Additional function requirements for no-load current management

Transition from circuit 15R to circuit 15C

The electronic ignition lock control unit sends the circuit 15 status over the interior CAN to the rear SAM control unit.

Function sequence for no-load current management

No-load current management ensures the engine's starting capability even after extended idle times. No-load current management is integrated into the rear SAM control unit.

Actuation of the no-load current management relay (F32k2) shuts off consumers that are supplied with power through circuit 30g.

No-load current management however, can accommodate increased power consumption for a specific period after switching off the engine (maximum t = 75 min.). This allows, for example, the radio to be played while the car is being washed.

No-load current management cyclically measures the voltage and power consumption every t = 6 minutes. If an excessively high no-load current is determined for a specific period, the no-load current management relay is opened at the earliest after t = 75 min., but no later than t = 6 h.

Following a period of t = 6 h or as soon as the on-board electrical system voltage drops below certain limits and thereby compromise the engine's starting capability, the extended run-on monitoring initiates the following measures:

Activation of no-load current management over CAN
Open no-load current shutoff relay

Before opening the no-load current switch relay a corresponding signal is sent over the CAN to shutdown the control units. This also authorizes, for example, the overhead control panel control unit (with CODE 414 (Power glass tilting/sliding roof)) to move an open tilting/sliding roof into the tilt position.

No-load current management encompasses the following subfunctions:

Function sequence for no-load current shutoff
Function sequence for no-load current diagnosis
No-load current reference value/residual charging current assessment function sequence

Function sequence for no-load current shutoff

No-load current management encompasses the following subfunctions:

Function sequence for requesting consumer shutoff (no-load current switch)
Function sequence for shut off consumers
Function sequence for energize consumers

Function sequence for requesting consumer shutoff (no-load current switch)

During the transition from circuit 15R to circuit 15C, the vehicle changes to the "vehicle rest" operating state.

The timer counting down to no-load current shutoff is then started (waiting time t = 6 h). The no-load current is continuously monitored by the battery sensor (B95). If the no-load current is too high, the no-load current shutoff relay will be opened at the earliest after t = 75 minutes. The rear SAM control unit reads in the data from the battery sensor over the on-board electrical system LIN (LIN B7) and evaluates it. If the on-board electrical system voltage drops within the waiting time to U < 11.8 V, the no-load current shutoff relay is prematurely opened.

If U < 11.8 V, the battery sensor will go into sleep mode (reduced power consumption).

T = 5 min before the opening of the no-load current shutoff relay, the rear SAM control unit sends a cutoff signal as advance notice to all control units supplied with power through circuit 30g.

The rear SAM control unit transmits this cutoff signal via interior CAN. The cutoff signal is received by the following control units:

Instrument cluster (A1)
Radio (with CODE 505 (Radio 20 NTG5 without navigation capability) or CODE 510 (Audio 20 with CD changer) or CODE 522 (Audio 20 radio) or CODE 523 (MB Audio 20 radio))
COMAND controller unit (with CODE 512 (COMAND APS incl. DVD changer) or CODE 526 (COMAND with single DVD drive (without navigation)) or CODE 527 (COMAND APS with single DVD drive (with navigation)) or CODE 528 (COMAND incl. DVD changer) or CODE 531 (COMAND APS))
Panoramic sliding sunroof control module (A98) (with CODE 413 (Panoramic glass sunroof with top sliding sunroof))
Pneumatic pump for dynamic multicontour seat (M40/1) (with CODE 432 (Left and right dynamic multicontour seat))
Front SAM control unit
Automatic air conditioning control and operating unit
Rear seat heater control unit (N25/6) (with CODE 872 (Electrically heated left and right rear seats))
Multifunction control unit for special-purpose vehicle (N26/9) (with CODE 965 (Electrical preinstallation for rental vehicles))
Trailer recognition control unit (N28/1) (with CODE 550 (Trailer hitch))
Driver seat control unit (N32/1) (with CODE 275 (Memory package for electrically adjustable front seats))
Front passenger seat control unit (N32/2) (with CODE 275 (Memory package for electrically adjustable front seats))
Left front dynamic multicontour seat control unit (N32/19) (with CODE 432 (Left and right dynamic multicontour seat))
Right front dynamic multicontour seat control unit (N32/22) (with CODE 432 (Left and right dynamic multicontour seat))
Left front door control unit
Right front door control unit
Left rear door control unit (N69/3)
Right rear door control unit (N69/4)
KEYLESS-GO control unit (N69/5) (with CODE 889 (Keyless-Go)) Overhead control panel control unit (N70) (with CODE 414 (Power glass tilting/sliding roof))
Electronic ignition switch control unit
Trunk lid control unit (N121) (model 212.0/1 with CODE 881 (Remote trunk closing (RTC [HDFS])))
Liftgate control unit (N121/1) (model 212.2)

The radio or the COMAND controller unit sends the shutoff signal via the telematics CAN (CAN A) to the following control units:

Navigation module (A2/30) (with CODE 509 (Navigation box))
Audio/COMAND display (A40/8)
Audio/COMAND control panel (A40/9)

The radio or the COMAND controller unit sends the shutoff signal via MOST to the following control units:

TV digital tuner (A90/3) (with CODE 865 (TV tuner))
Sound system amplifier control unit (N40/3) (with CODE 810 (Sound system) or CODE 811 (Advanced sound system))
Digital Audio Broadcasting control unit (N87/3) (with CODE 537 (Digital radio))
Satellite Digital Audio Radio (SDAR) control unit (N87/5) (with CODE 536 (SIRIUS satellite radio))
Media interface control unit (N125/1) (with CODE 518 (Media interface))

The front SAM control unit sends this shutdown signal via chassis CAN 1 and chassis CAN 2 (CAN E2).

The following control units receive the shutoff signal over the chassis CAN 1:

Left front reversible emergency tensioning retractor (A76)
Right front reversible emergency tensioning retractor (A76/1)
Supplemental restraint system control unit (N2/10)
CDI control unit or ME-SFI control unit
Transmission mode control unit (N145) (transmission 722.931)
Chassis gateway control unit (N93/7) (with CODE 23P (Driving assistance package Plus))

The chassis gateway control unit sends the shutoff signal via the chassis FlexRay (Flex E) to the following control units:

Stereo multifunction camera (A40/13) (with CODE 628 (AUTOMATIC HIGH BEAM CONTROL PLUS (IHC+)) or CODE 513 (Traffic sign recognition) and CODE 23P (Driving assistance package Plus))
Radar sensors control unit (N62/1) (with CODE 23P (Driving assistance package Plus))

The following control units receive the shutoff signal over chassis CAN 2:

Left headlamp control unit (E1n9)
Right headlamp control unit (E2n9)
Multifunction camera (A40/11) (with CODE 476 (Lane Keeping Assist) or CODE 513 (Traffic sign recognition) or CODE 628 (AUTOMATIC HIGH BEAM CONTROL PLUS (IHC+)) and except CODE 23P (Driving assistance package Plus))
Tire pressure monitor control unit (N88) (with CODE 475 (Tire pressure monitor (Premium)), Schrader)
Reversing camera (B84/3) (with CODE 218 (Reversing camera))
360° camera control unit (N148) (with CODE 501 (360 degree camera))

If the interior CAN, chassis CAN 1 and chassis CAN 2 are in "sleep mode" during signal transmission, the corresponding control units are activated. The control units will then prepare themselves for power supply shutoff.

Within t = 5 min., these control units will go into "power-down mode" (decentralized power management).

Function sequence for shut off consumers

Following a period of t = 5 min., no-load current management opens the no-load current shutoff relay provided no closing causing event has occurred in the meantime. The rear SAM control unit sends the switching status of the no-load current shutoff relay over the interior CAN. The front SAM control unit receives this information and transmits it via chassis CAN 1 and chassis CAN 2.

Function sequence for energize consumers

The no-load current management closes the no-load current shutoff relay as soon as a system is activated. All the functions are then available again.

The no-load current shutoff relay is opened again when the waiting time of t = 6 h has expired, the on-board electrical system voltage is less than U = 11.8 V or the no-load current is too high.

If the rear SAM control unit receives a wake-up signal, the no-load current management system closes the no-load current shutoff relay and signals via the interior CAN that the wake-up conditions for the control units are active again. The front SAM control unit receives this signal and sends it via chassis CAN 1 and chassis CAN 2. Closing the no-load current shutoff relay causes power to again be supplied via circuit 30g.

Detailed information on the signal flow is given in the chapter "Requesting consumer shutoff (no-load current switch)".

The following activities will trigger the closure of the no-load current shutoff relay:

Switching on circuit 15R
Unlocking or opening of a door or switching on circuit 15C
Switching on of the hazard warning system, the standing or parking lights or the signaling system of special-purpose vehicles
Activation of anti-theft alarm system (ATA) (with CODE 551 (Anti-theft alarm system (ATA)))
Triggering of panic alarm (with CODE 763 (Radio remote control with panic switch))
Activation of stationary heater (with CODE 228 (Stationary heater))

Function sequence for no-load current diagnosis

No-load current diagnosis records data to help troubleshoot possible fault profiles.

No-load current diagnosis function encompasses the following subfunctions:

Function sequence for activating no-load current diagnosis
Function sequence for terminating/ending no-load current diagnosis

Additional function requirements for activating no-load current

Circuit 15R OFF

Function sequence for activating no-load current diagnosis

The battery sensor starts the no-load current diagnosis via the on-board electrical system LIN, if one of the following events occurs:

Increased no-load current following expiration of tolerance time of t = 75 min.
On-board electrical system voltage values fall below limits and there has been a change in the kilometer reading since the last fault roll entry caused by undervoltage (also before expiration of tolerance time of t = 75 min.)

With the first waking event an entry in the no-load current fault roll takes place. Following this, the no-load current is cyclically checked. These values are updated if there are significant changes or if the no-load current diagnosis is canceled.

The following data are stored in nonvolatile memory in the no-load current fault roll:

No-load current value upon occurrence of wake-up event

Maximum no-load current during no-load current fault phase
Minimum no-load current during no-load current fault phase
Voltage of on-board electrical system battery upon occurrence of wake-up event
Voltage of on-board electrical system battery at end of no-load current fault phase
Duration of no-load current fault phase (in minutes)
Kilometer reading
Consumer status

As long as no-load current diagnosis is active, each additional battery sensor wake-up event will cause the data record to be updated.

Additional function requirement for aborting/terminating no-load current diagnosis

Circuit 15R ON

Function sequence for terminating/ending no-load current diagnosis

The no-load current diagnosis is aborted if the limits (U < 11.8 V) for the on-board electrical system voltage are undershot. The battery sensor will discontinue no-load current monitoring in order to minimize electricity consumption. Once this happens, no further entries will be added to the quiescent current fault roll.

Additional function requirements for no-load current reference value/residual charging current assessment

Circuit 30 ON

No-load current reference value/residual charging current assessment function sequence

After the vehicle has gone through production testing and possible runs on the test track, the no-load current has to be measured and an assessment made of the residual charge current of the on-board electrical system battery.

The no-load current-reference value/residual charging current encompasses the following subfunctions:

No-load current reference value measurement function sequence
Function sequence for residual charge current assessment

No-load current reference value measurement function sequence

The measurement of the no-load current reference value is started using the diagnostic-tester at circuit 15R or higher.

The message "Measure no-load current!" appears in the multifunction display (A1p13) of the instrument cluster. The diagnostic tester must then be removed and the vehicle locked so that the vehicle's no-load current will quickly drop. The battery sensor will then sense and save the maximum no-load current level to occur following the locking of the vehicle.

After the vehicle is woken up, the battery sensor sends the measured no-load current value via the on-board electrical system LIN to the rear SAM control unit, which then saves it as the no-load current reference value in nonvolatile memory.

The no-load current reference value can be read out using the diagnostic tester.

If the measured no-load current is within a defined tolerance range, the message in the multifunction display will disappear. If the no-load current reference value is too high, a fault message will be shown in the multifunction display of the instrument cluster and measurement will begin again.

Function sequence for residual charge current assessment

During production, charge is removed from the battery in the course of various function tests. The charge level of the on-board electrical system battery must therefore be assessed at the end of assembly. The charge level (ratio of current charge to the maximum storable charge) serves as the measure for a sufficiently charged on-board electrical system battery. This value must be above 80%.

If the charge level is below 80%, a fault message will be shown in the multifunction display of the instrument cluster. Measurement of the residual charge current is only done following successful measurement of the no-load current reference value. As a rule, the two values are released together.

Function sequence for remote charging/jump start

If the on-board electrical system battery does not have enough capacity to start the engine, the on-board electrical system battery must be charged or a jump start carried out.

One of the front doors must be opened during a jump-start procedure or during any testing in the workshop to enable the alternator management (except model 212.095) to change to the jump-start or workshop mode and the alternator voltage to be increased to U = 14.3 V.

MODEL 212.095/098/298

as of model year 2014

If the battery output of the high-voltage battery (A100g1) is very low (P < 8 kW) when starting the drive system, startability can be established by an energy transfer from the 12 V on-board electrical system to the high-voltage on-board electrical system.

If, when the engine hood is open, an external charger is connected and the power electronics control unit (N129/1) measures voltage of more than U = 12.8 V in the 12 V on-board electrical system, energy with a maximum power of P = 500 W is transferred over the on-board electrical system battery and the power electronics control unit to the high-voltage on-board electrical system and the high-voltage battery is charged (with circuit 15 ON only).

	Electrical function schematic for no-load current management		PE54.10-P-2074-97DAA
	Electrical function schematic for comfort function shutoff		PE54.10-P-2074-97DAA
	Overview of energy management system components		GF54.10-P-9990FLM