Engine Off Energy Management, Function - GF54.10-P-1050LF

Model 217, 222

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 control unit (N3/10) (gasoline engine) sends the "engine running" or "drive train operational" signal via the drive train CAN (CAN C1), powertrain control unit (N127), suspension FlexRay (Flex E), electronic ignition lock control unit (N73) and interior CAN (CAN B) to the front SAM control unit (N10/6).

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 functionality is integrated in the front SAM control unit and serves to extend the service life of the on-board electrical system battery (G1). To this end, active comfort functions or consumers are switched off.

Engine OFF energy management encompasses the following subfunctions:

Function sequence for consumer reduction (deactivation of convenience functions)
Function sequence for deep discharge protection (model 217 as of 01.12.2017, model 222 as of 01.06.2017)
Function sequence for quiescent current management (model 217 up to 30.11.2017, model 222 up to 31.05.2017)
Function sequence for remote charging/jump start

Additional function requirement for consumer reduction (deactivation of comfort functions)

Circuit 15 ON or circuit 15R ON

The electronic ignition lock control unit sends the status of terminal 15 to the front SAM control unit over the interior CAN.

Function sequence for consumer reduction (deactivation of convenience functions)

If the on-board electrical system voltage drops to below U = 11.8 V for t = 5 s, the front SAM control unit activates the consumer reduction function (deactivation of comfort functions) and sends the request for output limitation or to deactivate consumers over the interior CAN to the corresponding control units that are connected to the interior CAN, and over the interior CAN, electronic ignition lock control unit and the suspension FlexRay to the steering column tube module control unit (N80) and over the interior CAN, electronic ignition lock control unit, suspension FlexRay, powertrain control unit and powertrain CAN to the CDI control unit or to the ME-SFI [ME] control unit. In model 217 as of 01.12.2017 and model 222 as of 01.06.2017, the front SAM control unit transmits this request to the head unit (A26/17) via the interior CAN, electronic ignition lock control unit and user interface CAN (CAN HMI).

Model 222.004/057/104/157/163/173

The energy requirement of the active consumers is initially provided by the energy transfer from the high-voltage on-board electrical system to the 12 V on-board electrical system until the charge level of the high-voltage battery (A100g1) drops below a defined limit value.

Model 222

with code B01 (48V technology)

The energy requirement of the active consumers is initially provided through transferring energy from the 48 V on-board electrical system to the 12 V on-board electrical system until the charge level of the 48 V battery drops below a defined limit value.

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 table below. The list includes those consumers whose power supply is reduced or shut off as part of the engine ON energy management function (up to shutoff stage 20).

Sequence	Shutoff stage	Power-reduced or deactivated function	Responsible control unit
1	1	PTC 1st branch, heat boosting (engine 642, 651)	Climate control control unit (N22/1)
2	2	PTC 2nd branch, heat boosting (engine 642, 651)	Climate control control unit (N22/1)
3	3	PTC 3rd branch, heat boosting (engine 642, 651)	Climate control control unit (N22/1)
4	4	PTC 4th branch, heat boosting (engine 642, 651)	Climate control control unit (N22/1)
5	5	PTC 5th branch, heat boosting (engine 642, 651)	Climate control control unit (N22/1)
6	6	PTC 6th branch, heat boosting (engine 642, 651)	Climate control control unit (N22/1)
7	7	Windshield heater (with code 597 (Heated windshield)) P = 50 %	Climate control control unit (N22/1)
8	8	Rear refrigerator box (with CODE 308 (Refrigerated compartment))	Rear SAM control unit (N10/8)
9	8	Wiper park heater	Front SAM control unit (N10/6)
10	9	Spray nozzle hose heater, wiper blade heater (with CODE 874 (MAGIC VISION CONTROL, heated))	Front SAM control unit (N10/6)
11	10	Mirror heater	Left front door control unit (N69/1) and right front door control unit (N69/2)
12	11	Seat heater, wall heating stage 3 (with code 401 (Seat climate control for driver and front passenger) or code 873 (Seat heater for driver and front passenger) or code 432 (Left and right dynamic multicontour seat))	Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
13	12	Rear window heater	Rear SAM control unit (N10/8)
14	13	Steering wheel heater (with CODE 443 (Steering wheel heater))	Steering column tube module control unit (N80)
15	14	Seat heater, wall heating stage 2 (with code 401 (Seat climate control for driver and front passenger) or code 873 (Seat heater for driver and front passenger) or code 432 (Left and right dynamic multicontour seat))	Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
16	15	Blower in rear (with CODE 582 (Air conditioning system in rear)) P = 50 %	Climate control control unit (N22/1)
17	16	Blower in front P = 50%	Climate control control unit (N22/1)
18	17	Fan P = 50%	CDI control unit (N3/9) (diesel engine) or ME-SFI [ME] control unit (N3/10) (gasoline engine)
19	18	Trunk socket, cigarette lighter (with CODE 301 (Smoker package))	Front SAM control unit (N10/6)
20	19	Windshield heater (with CODE 597 (Heated windshield)) P = 0 %	Climate control control unit (N22/1)
21	20	Seat heater, wall heating stage 1 (with CODE 401 (Seat climate control for driver and front passenger) or CODE 873 (Seat heater for driver and front passenger) or CODE 432 (Left and right dynamic multicontour seat))	Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
22	20	Seat ventilation (with CODE 401 (Seat climate control for driver and front passenger))	Driver's seat control unit (N32/1), front passenger seat control unit (N32/2)
23	21	Residual heat utilization of engine	Climate control control unit (N22/1)
24	22	Blower in rear (with CODE 582 (Air conditioning system in rear)) P = 0 %	Climate control control unit (N22/1)
25	23	Stationary heater (with CODE 228 (Stationary heater))	Stationary heater control unit (A6n1)
26	24	Telematics, audio, telephone, GPS (model 217 up to 30.11.2017, model 222 up to 31.05.2017)	COMAND controller unit (A40/3)
26	24	Telematics, audio, telephone, GPS (model 217 as of 01.12.2017, model 222 as of 01.06.2017)	Head unit (A26/17)

Even when the on-board electrical system voltage stabilizes at a value in excess of U = 11.8 V, the output limitation or shutoff of consumers is not canceled. The output limitation or shutoff of consumers is only canceled again after an engine start.

Function sequence for deep discharge protection (model 217 as of 01.12.2017, model 222 as of 01.06.2017)

Deep discharge protection prevents excessive discharging of the on-board electrical system battery when the vehicle is at a standstill (rest phase). This ensures that startability of the engine is retained over a long period of time or at increased no-load currents. Furthermore, increased no-load currents resulting from hardware resets caused by defective components are also minimized. The function is integrated in the front SAM control unit (energy management) and in the electronic ignition lock control unit (closing and security).

The deep discharge protection function comprises the following subfunctions:

Quiescent current reference value/residual charging current evaluation (model 217 as of 01.12.2017, model 222 as of 01.06.2017)
Quiescent current shutoff (model 217 as of 01.12.2017, model 222 as of 01.06.2017)

Additional function requirements for quiescent current reference value/residual charging current evaluation (model 217 as of 01.12.2017, model 222 as of 01.06.2017)

Circuit 15R ON

The electronic ignition lock control unit sends the status of terminal 15 to the front SAM control unit over the interior CAN.

Quiescent current reference value/residual charging current evaluation (model 217 as of 01.12.2017, model 222 as of 01.06.2017)

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.

Measurement of the no-load current reference value is started via the diagnostic tester. The message "Measure no-load current!" appears in the instrument cluster (A1). The front SAM control unit sends the request to display the message to the instrument cluster via the interior CAN, electronic ignition lock control unit and the user interface CAN. The diagnostic tester must then be removed and the vehicle locked so that the vehicle's no-load current will quickly drop.

The minimum no-load current which has occurred since locking is continuously captured by the battery sensor (B95) (except code U98 (LITHIUM-ION STARTER BATTERY (LISB))) or by the control electronics in the on-board electrical system battery (with CODE U98 (LITHIUM-ION STARTER BATTERY (LISB))) and stored. After the vehicle has "woken up", the battery sensor or the control electronics in the on-board electrical system battery sends the measured no-load current value via the battery sensor LIN (LIN B15) to the front SAM control unit, which then saves this value as the no-load current reference value in the non-volatile 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 instrument cluster goes out.

If the no-load current reference value is too high, a no-load current fault message appears in the instrument cluster and measurement is started again.

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 in the on-board electrical system battery) 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 is shown in 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.

Additional function requirements for quiescent current shutoff (model 217 as of 01.12.2017, model 222 as of 01.06.2017)

Circuit 15R OFF

The electronic ignition lock control unit sends the status of terminal 15 to the front SAM control unit over the interior CAN.

Quiescent current shutoff (model 217 as of 01.12.2017, model 222 as of 01.06.2017)

The no-load current shutoff prevents deep discharge of the on-board electrical system battery and is started under the following conditions:

High no-load current
Charge level of on-board electrical system battery < 40 % (not for vehicles with code B01 (48V technology) and not for vehicles with code 882 (interior monitoring) in locked condition)

The charge level of the on-board electrical system battery and the on-board electrical system load are captured by the battery sensor or by the control electronics in the on-board electrical system battery.

The battery sensor or the control electronics in the on-board electrical system battery communicate with the front SAM control unit via the on-board electrical system LIN.

If one of the conditions for activation of the quiescent current shutoff occurs, the front SAM control unit actuates the relay for the battery disconnect switch (F33k3) in the rear prefuse box (F33) after expiry of 10 minutes towards open. Beforehand, the front SAM control unit sends a signal via the interior CAN as advance notice of shutoff. This signal is relevant for all control units that are supplied with voltage via circuit 30t. All consumers that are supplied with voltage via circuit 30t are then switched off.

The following events prevent opening of the battery disconnect switch relay:

Change in circuit status (circuit 15R ON or circuit 15 ON)
Hazard warning flasher function active
Anti-theft alarm system (ATA) alarm (with code 551 (Anti-theft alarm system (ATA)))
Active panic alarm (with code 763 (Radio remote control with panic switch))
External charging
Remote start active (with code 05U (Remote online))

If the battery disconnect switch relay was opened due to the charge level of the on-board electrical system battery, it remains open permanently.

On vehicles with code 05U (Remote online), if the on-board electrical system battery reaches a critical charge level, the energy management sends a corresponding message to the vehicle owner before the battery disconnect switch relay is opened. The vehicle owner then has the option of initiating jump-starting via a mobile phone. When jump-starting is performed, the front SAM control unit activates all shutoff stages of the consumer reduction function in order to achieve maximum charging of the on-board electrical system battery.

If the battery disconnect switch relay was opened due to excessive no-load current, the electronic ignition lock control unit control unit actuates the battery disconnect switch relay in the close direction after a defined period of time has expired. All consumers on circuit 30t are then supplied with voltage again.

The brief opening of the battery disconnect switch relay may cause resetting of the no-load current consumers (hardware reset). If the no-load current is still too high, the battery disconnect switch relay is opened and closed again a maximum of two more times. If the no-load current is still too high, the battery disconnect switch relay remains closed permanently.

Increased no-load currents owing to an active application or function (e.g. radio, standing lights, stationary heater (with code 228 (Stationary heater)), evaporator drying) are permitted and do not cause the battery disconnect switch relay to open.

The battery disconnect switch relay is closed again if one of the following events occurs:

Unlocking of the central locking
Change in circuit status (circuit 15R ON or circuit 15 ON)
Diagnostic command from the electronic ignition lock control unit

Model 217

as of model year 2018

Model 222

as of model year 2018

except code B01 (48V technology)

The no-load current shutoff can also be triggered manually via a corresponding menu in the head unit (rest mode). In this case, all electrical consumers that are supplied with voltage via circuit 30t are switched off 15 min after the ignition is switched off. The remaining service life in weeks is then shown in the Audio/COMAND display (A40/8). If the rest mode cannot be started due to an active fault, the message "Function not available!" appears. If the rest mode cannot be started due to the charge level of the battery, the message "Charge level too low for rest mode" appears.

The head unit sends the "Activate rest mode" request via the user interface CAN, electronic ignition lock control unit and interior CAN to the front SAM control unit, which then starts the no-load current shutoff. The front SAM control unit then sends information for displaying the remaining service life or for outputting the message via the interior CAN, electronic ignition lock control unit and user interface CAN to the head unit. The head unit then actuates the display in the Audio/COMAND display via the high speed video link signal line.

Additional function requirements for quiescent current management (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

Transition from circuit 15R to circuit 15C

The electronic ignition lock control unit sends the status of terminal 15 to the front SAM control unit over the interior CAN.

Function sequence for quiescent current management (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

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

Actuation of the no-load current shutoff relay (F32/4k2) in the vehicle interior prefuse box (F32/4) shuts off the consumers that are powered through terminal 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.

After a period of t = 6 h or as soon as the limit value for the on-board electrical system voltage (except engine 157, 279) or for the charge level of the on-board electrical system battery (engine 157, 279) has been undershot and the starting capability of the engine is therefore at risk, the following measures are initiated:

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

Before the no-load current shutoff relay is opened, the front SAM control unit sends a corresponding signal to reduce the power of the control units via CAN. For example, this also authorizes the panoramic sliding sunroof control unit (A98n1) (with CODE 413 (Panoramic sliding sunroof)) to move an open panoramic roof to the tilt position.

The no-load current management system comprises the following subfunctions:

Function sequence for quiescent current shutoff (model 217 up to 30.11.2017, model 222 up to 31.05.2017)
Function sequence for quiescent current diagnosis (model 217 up to 30.11.2017, model 222 up to 31.05.2017)
Function sequence for quiescent current reference value/residual charging current evaluation (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

Function sequence for quiescent current shutoff (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

The no-load current shutoff system function comprises the following subfunctions:

Requesting function sequence for consumer shutoff (no-load current switch) (model 217 up to 30.11.2017, model 222 up to 31.05.2017)
Shutting off function sequence for consumer (model 217 up to 30.11.2017, model 222 up to 31.05.2017)
Switching on function sequence for consumer (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

Requesting function sequence for consumer shutoff (no-load current switch) (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

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 quiescent current is detected continuously by the battery sensor (except engine 157, 279) or by the control unit in the on-board electrical system battery (engine 157, 279). 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 front SAM control unit reads in the data from the battery sensor or the data from the control unit in the on-board electrical system battery over the battery sensor LIN and evaluates it.

If the on-board electrical system voltage drops to U < 11.8 V within the waiting time (except engine 157, 279) or if the permissible discharge current of the on-board electrical system battery is exceeded (engine 157, 279), 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). The control unit in the on-board electrical system battery goes into sleep mode (reduced power consumption) depending on the current.

At t = 5 min before the no-load current shutoff relay is opened, the front SAM control unit sends a shutoff signal as advance notice to all control units supplied with power via terminal 30g.

The front SAM control unit sends this shutoff signal via the interior CAN.

The following control units receive the shutoff signal via the interior CAN:

Panoramic sliding sunroof control unit (with CODE 413 (Panoramic sliding sunroof))
Multicontour seat pneumatic pump (M40) (with CODE 432 (Left and right dynamic multicontour seat) or model 222 with CODE 406 (Rear multicontour seats))
Active belt buckle control unit (N2/3) (with CODE 305 (Rear PRE-SAFE))
Climate control control unit (N22/1)
Rear control unit (N22/6) (model 217)
ATA/tow-away protection/interior protection control unit (N26/6) (with CODE 882 (Interior monitoring))
Trailer recognition control unit (N28/1) (with CODE 550 (Trailer hitch))
Driver's seat control unit (N32/1)
Front passenger seat control unit (N32/2)
Right rear seat control unit (N32/5) (with CODE 223 (Electrically adjustable rear bench seat))
Left rear seat control unit (N32/6) (with CODE 223 (Electrically adjustable rear bench seat))
Left front dynamic multicontour seat control unit (N32/15) (with CODE 432 (Left and right dynamic multicontour seat))
Right front dynamic multicontour seat control unit (N32/16) (with CODE 432 (Left and right dynamic multicontour seat))
Left rear multicontour seat control unit (N32/20) (model 222 with CODE 406 (Multicontour seats in rear))
Right rear multicontour seat control unit (N32/21) (model 222 with CODE 406 (Multicontour seats in rear))
Camera cover control unit (N42) (model 217 or model 222 with code 218 (Reversing camera) or with code 501 (360° Camera))
Left front door control unit (N69/1)
Right front door control unit (N69/2)
Left rear door control unit (N69/3) (model 222)
Right rear door control unit (N69/4) (model 222)
KEYLESS-GO control unit (N69/5)
Electronic ignition switch control unit
Trunk lid control (KDS) control unit (N121) (model 217 or model 222 with CODE 881 (Remote trunk closing))

The electronic ignition lock control unit sends the shutoff signal over the suspension FlexRay to the following control units:

Stereo multifunction camera (A40/13) (with code 487 (Active Body Control (ABC)), code 513 (Traffic Sign Assist), code 610 (Night View Assist) or code 608 (Adaptive Highbeam Assist) or code 628 (Adaptive Highbeam Assist Plus) and code P20 (Driving Assistance Plus Package))
Active Body Control control unit (N51/2) (with CODE 487 (Active Body Control (ABC)))
AIRmatic control unit (N51/3) (except CODE 487 (Active Body Control (ABC)))
Electronic Stability Program control unit (N30/4)
Parking system control unit (N62) (with code 235 (Active Parking Assist) or with code 501 (360° Camera))
Radar sensors control unit (N62/1) (with CODE P20 (Driving assistance package Plus))
Steering column module control unit

The electronic ignition lock control unit sends the shutoff signal over the user interface CAN to the following control units:

COMAND controller unit (A40/3)
Head-up display (A40/12) (with CODE 463 (Head-up display))
Left front reversible emergency tensioning retractor (A76)
Right front reversible emergency tensioning retractor (A76/1)
Reversing camera control unit (N66/2) (model 217 or model 222 with code 218 (Reversing camera) or with code 501 (360° Camera))
Tire pressure monitoring system control unit (N88) (with code 475 (Tire pressure monitoring system)
360° camera control unit (N148) (with CODE 501 (360° camera))

The electronic ignition lock control unit sends the shutoff signal over the periphery CAN to the following control units:

Mono multifunction camera (A40/11) (with code 513 (Traffic Sign Assist), code 610 (Night View Assist) or code 608 (Adaptive Highbeam Assist) or code 628 (Adaptive Highbeam Assist Plus) and except code P20 (Driving Assistance Plus Package))
Drivetrain control unit

The powertrain control unit sends the shutoff signal to the following control unit via drive train CAN:

Intelligent servo module for DIRECT SELECT (A80)

The following control units receive the shutoff signal via MOST:

Rear Seat Entertainment system controller unit (A26/18) (with CODE 864 (Rear Seat Entertainment system))
Tuner unit (A90/4) (with CODE 536 (SIRIUS satellite radio) or CODE 537 (Digital radio (DAB)) or CODE 865 (TV tuner))
Sound system amplifier control unit (N40/3) (with CODE 810 (Sound system) or CODE 811 (Advanced sound system))

The following control units receive the shutoff signal via the telematics CAN:

Left rear display (A40/5) (with CODE 864 (Rear Seat Entertainment system))
Right rear display (A40/6) (with CODE 864 (Rear Seat Entertainment system))
Audio/COMAND display
Audio/COMAND control panel (A40/9)
Touchpad (A105) (with CODE 448 (Touchpad))

If a CAN is in "sleep mode" during signal transmission, the corresponding control units are woken up. 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).

Shutting off function sequence for consumer (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

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 front SAM control unit sends the status of the no-load current shutoff relay via the interior CAN.

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

Switching on function sequence for consumer (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

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 drops to below U = 11.8 V or the permissible discharge current of the on-board electrical system battery is exceeded. If the front 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. 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 on Requesting consumer shutoff (no-load current switch).

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

Switching on terminal 15R
Unlocking or opening of a door or the trunk lid or switching on of the terminal 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 quiescent current diagnosis (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

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

The no-load current diagnosis function comprises the following subfunctions:

Activating function sequence for quiescent current diagnosis (model 217 up to 30.11.2017, model 222 up to 31.05.2017)
Canceling/stopping function sequence for quiescent current diagnosis (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

Activating additional function requirements for quiescent current diagnosis (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

Circuit 15R OFF

The electronic ignition lock control unit sends the status of terminal 15 to the front SAM control unit over the interior CAN.

Activating function sequence for quiescent current diagnosis (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

The battery sensor or the control unit in the on-board electrical system battery starts the no-load current diagnosis via battery sensor LIN if one of the following events takes place:

Increased no-load current following expiration of tolerance time of t = 75 min.
The on-board electrical system voltage falls below the limit value, or the permissible discharge current of the on-board electrical system battery has been exceeded and there has been a change in the kilometer reading since the last fault roll entry caused by undervoltage or excessive discharge current of the on-board electrical system battery (even before expiration of the 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.

The values will be 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 or the control unit in the on-board electrical system battery will cause the data record to be updated.

Canceling/stopping additional function requirements for quiescent current diagnosis (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

Circuit 15R ON
On-board electrical system voltage values fall below limits or the permissible discharge current of on-board electrical system battery has been exceeded

The electronic ignition lock control unit sends the status of terminal 15 to the front SAM control unit over the interior CAN.

Canceling/stopping function sequence for quiescent current diagnosis (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

The no-load current diagnosis is canceled if the on-board electrical system voltage drops below the limit value (U <11.8 V) or the permissible discharge current of the on-board electrical system battery is exceeded. The battery sensor or the control unit in the on-board electrical system battery will discontinue no-load current monitoring in order to minimize electricity consumption. Once this happens, no further entries will be added to the fault roll.

Additional function requirements for quiescent current reference value/residual charging current evaluation (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

Circuit 30 ON

Function sequence for quiescent current reference value/residual charging current evaluation (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

The no-load current reference value/residual charging current evaluation function comprises the following subfunctions:

Function sequence for measurement of quiescent current reference value (model 217 up to 30.11.2017, model 222 up to 31.05.2017)
Function sequence for residual charging current evaluation (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

Function sequence for measurement of quiescent current reference value (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

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 instrument cluster. This request is sent by the front SAM control unit via interior CAN, electronic ignition lock control unit and the user interface CAN to 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 or the control unit in the on-board electrical system battery will then record and save the minimum no-load current level to occur following the locking of the vehicle. After the vehicle has "woken up", the battery sensor or the control unit in the on-board electrical system battery sends the measured no-load current value via battery sensor LIN to the front SAM control unit, which then saves it as the no-load current reference value in the 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 instrument cluster goes out.

If the no-load current reference value is too high, a fault message appears in the instrument cluster and measurement is started again.

Function sequence for residual charging current evaluation (model 217 up to 30.11.2017, model 222 up to 31.05.2017)

This value must be above 80%. If the charge level is below 80 %, a fault message is shown in 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.

Model 222.004/057/104/157/163/173

If the battery output of the high-voltage battery is very low (P < 8 kW) when starting the hybrid drive system, the starting capability can be established through 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 measures a voltage of more than 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 (only with terminal 15 ON).

Model 222

with code B01 (48V technology)

If the battery output of the 48 V battery is very low when the engine is started (P < 5.2 kW), the starting capability can be established by transferring energy from the 12 V on-board electrical system to the 48 V on-board electrical system.

If an external charger is connected and the DC/DC converter control unit measures a voltage higher than 12.8 V in the 12 V on-board electrical system, then energy is transferred at a maximum output of 500 W over the DC/DC converter control unit into the 48 V on-board electrical system and the 48 V battery is charged.

Direct charging of 48 V on-board electrical system battery, e.g. using a 48 V charger is not intended and it could damage the 48 V on-board electrical system battery.

Electrical function schematic for no-load current management	Model 217, 222 as of model year 2018	PE54.10-P-2074-97SEB
	Model 217, 222 up to model year 2018	PE54.10-P-2074-97SEA
Electrical function schematic for comfort function shutoff		PE54.10-P-2076-97SEA
Overview of energy management system components		GF54.10-P-9990LF