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Home >> Mercedes Benz >> 2013 >> CLS63 >> Repair and Diagnosis >> Electrical >> Gauges >> Electrical System, Equipment & Instructions - 218 Chassis - 1 Of 4 >> Basic Knowledge >> Engine off energy management, function >> Engine off energy management, function - GF54.10-P-1050FQ

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

MODEL 218 

Function requirements, general 

IMPORTANT The CDI control unit (N3/9) (with diesel engine) or the ME-SFI control unit (N3/10) (with gasoline engine) sends the "Engine running" or "Drivetrain operational" signal via the chassis CAN (CAN E) (until 28.02.2013) or chassis CAN 1 (CAN E1) (from 01.03.2013), front SAM control unit with fuse and relay module (N10/1) and 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 vehicle when the engine is off. This functionality is integrated into the rear 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:

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

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

Function sequence for consumer reduction (deactivation of convenience functions) 

If the on-board electrical system voltage for t = 5 s sinks to below U = 11.8 V, the rear SAM control unit activates the consumer reduction function (switching off of comfort functions). To do so, it sends the request to reduce output or shut off consumers via the interior CAN to the corresponding control units connected at the interior CAN and via the interior CAN, front SAM control unit and chassis CAN 1 (CAN E1) (from 01.03.2013) to the steering column tube module control unit (N80).

The state of the on-board electrical system battery (G1) is recorded by the battery sensor (B95). The battery sensor sends corresponding parameters of the on-board electrical system battery via the on-board electrical system LIN (LIN B7) to the rear SAM control unit. The rear SAM control unit evaluates all relevant information and activates the consumer reduction function (switching off of comfort functions).

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 from 01.06.2012 is shown in the table below. 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 Consumers with reduced or no power Responsible control unit Maximum current in A
1 1 Heating level 6, heat boosting on passenger side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
2 2 Heating level 5, heat boosting on driver side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
3 3 Heating level 4, heat boosting on passenger side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
4 4 Heating level 3, heat boosting on driver side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
5 5 Heating level 2, heat boosting on passenger side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
6 6 Heating level 1, heat boosting on driver side (with engine 642.8, 651.9) 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
10 10 Mirror heater Left front door control unit (N69/1) and right front door control unit (N69/2) 3.5
11 11 Steering wheel heater (with code (443) Steering wheel heater) Steering column tube module control unit (N80) 8.0
12 12 Rear window heater Rear SAM control unit with fuse and relay module (N10/2) 30.0
13 13 Rear blower (with code (581) comfort automatic air conditioning) P = 50 % Automatic climate control and operating unit (N22/7) 5.5
14 14 Blower in front P = 50% Automatic climate control and operating unit (N22/7) 16.0
15 15 Fan P = 50% Automatic climate control and operating unit (N22/7) 31.0
16 16 Circuit 15R relay (1) (N10/2kB) Rear SAM control unit with fuse and relay module (N10/2) 6
17 18 Seat heater stage 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
18 19 Residual heat utilization (with code (581) Comfort automatic air conditioning and without code (494) USA version) Automatic climate control and operating unit (N22/7) 8
    Rear air conditioning (with code (581) comfort automatic air conditioning)   6
19 20 Stationary heater (with code (228) Stationary heater) Stationary heater control unit (A6n1) 10
20 21 Audio system Radio (A2) (until 31.08.2014 with code (523) MB Audio 20 radio or code (510) Audio 20 incl. CD changer, from 01.09.2014 with code (505) Radio 20 NTG5, without navigation function, or code (522) Audio 20 radio)
COMAND controller unit (A40/3) (until 31.08.2014 with code (512) COMAND APS incl. DVD changer, code (527) COMAND APS with single DVD drive (with navigation function) or code (528) COMAND incl. DVD changer, from 01.09.2014 with code (531) COMAND APS)
2

The shutoff sequence until 31.05.2012 is shown in the table below. 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 18).

Shutoff step Shutoff stage Consumers with reduced or no power Responsible control unit Maximum current in A
1 1 Heating level 6, heat boosting on passenger side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
2 2 Heating level 5, heat boosting on driver side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
3 3 Heating level 4, heat boosting on passenger side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
4 4 Heating level 3, heat boosting on driver side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
5 5 Heating level 2, heat boosting on passenger side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
6 6 Heating level 1, heat boosting on driver side (with engine 642.8, 651.9) Automatic climate control and operating unit (N22/7) 18.5
7 7 Rear blower (with code (581) comfort automatic air conditioning) P = 50 % Automatic climate control and operating unit (N22/7) 5.5
8 8 Blower in front P = 50% Automatic climate control and operating unit (N22/7) 16.0
9 9 Fan P = 50% Automatic climate control and operating unit (N22/7) 31.0
10 11 Circuit 15R relay (1) (N10/2kB) Rear SAM control unit with fuse and relay module (N10/2) 6
11 12 Seat ventilation (with code (401) Front comfort seats, incl. seat heating and seat ventilation) Rear SAM control unit with fuse and relay module (N10/2) 2.2
13 13 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
14 14 Rear window heater Rear SAM control unit with fuse and relay module (N10/2) 30.0
15 15 Wiper park heater Front SAM control unit with fuse and relay module (N10/1) 15
16 16 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
17 17 Seat heater stage 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
18 18 Steering wheel heater (with code (443) Steering wheel heater) Steering wheel heater control unit (N25/7) 8.0
19 20 Mirror heater Left front door control unit (N69/1) and right front door control unit (N69/2) 3.5
20 21 Residual heat utilization (with code (581) Comfort automatic air conditioning and without code (494) USA version) Automatic climate control and operating unit (N22/7) 8
    Rear air conditioning (with code (581) comfort automatic air conditioning)   6
21 22 Comfort lamps in the rear Front SAM control unit with fuse and relay module (N10/1) and
Overhead control panel control unit (N70) (with code (414) Power glass tilting/sliding sunroof)
1
    Trunk illumination, interior illumination Rear SAM control unit with fuse and relay module (N10/2) 0.5
22 24 Stationary heater (with code (228) Stationary heater) Stationary heater control unit (A6n1) 10
23 25 Audio system Radio (A2) (with code (523) Radio MB Audio 20 or code (510) Audio 20 with CD changer)
Radio with autopilot system (A2/56) (with code (525) MB Audio 50 APS radio or code (511) Audio 50 APS with DVD changer)
COMAND controller unit (A40/3) (with code (512) COMAND APS incl. DVD changer, code (526) COMAND with single DVD drive (without navigation function), code (527) COMAND APS with single DVD drive (with navigation function) or code (528) COMAND incl. DVD changer)
2

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

Additional function requirements for no-load current management 

IMPORTANT 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 vehicle'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 shutoff relay (F32k2) in the front prefuse box (F32) shuts off consumers that are supplied with voltage via circuit 30g. The actuation of the no-load current shutoff relay is carried out via the rear SAM control unit.

The no-load current management 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 shutoff relay is opened by the no-load current management at the earliest after t = 75 min., but no later than t = 6 h. After a time of t = 6 h has elapsed, or as soon as specific limits for the on-board electrical system voltage are undershot, causing the starting ability of the engine to be jeopardized, the following steps are taken:

Before the no-load current shutoff relay is opened, the rear SAM control unit sends a corresponding signal to reduce the power of the control units via the interior CAN. This in turn, authorizes e.g. the overhead control panel control unit to move an open tilting/sliding roof to the tilt position.

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

Function sequence for no-load current shutoff 

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

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 recorded by the battery sensor. 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 via the on-board electrical system LIN and evaluates these data. 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.

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

The rear SAM control unit sends a shutoff signal t = 5 min. before opening the no-load current shutoff relay as advance notice via the interior CAN. This shutoff signal is relevant to all control units receiving power via circuit 30g.

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

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

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

The front SAM control unit sends the shutoff signal via the chassis CAN (until 28.02.2013) to the following control units:

The front SAM control unit sends the shutoff signal via the chassis CAN 1 (from 01.03.2013) to the following control units:

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

The front SAM control unit sends the shutoff signal via the chassis CAN 2 (from 01.03.2013) to the following control units:

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).

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.

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

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 the chassis CAN (until 28.02.2013) or chassis CAN 1 (from 01.03.2013) and chassis CAN 2 (from 01.03.2013). Closing the no-load current shutoff relay causes power to again be supplied via circuit 30g.

IMPORTANT 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:

Function sequence for no-load current diagnosis 

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

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

Additional function requirements for activating no-load current 

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

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:

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:

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 requirements for canceling/ending no-load current diagnosis 

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

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 charge current assessment 

Function sequence for no-load current reference value/residual charge current assessment 

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 evaluation function comprises the following subfunctions:

Function sequence for measurement of no-load current reference value 

The measurement of the no-load current is started via 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 rear SAM control unit sends the request to display various messages via the interior CAN to the instrument cluster. The minimum no-load current occurring since locking is recorded and stored by the battery sensor.

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.

IMPORTANT If the measured no-load current is within a defined tolerance range, the message in the multifunction display on the instrument cluster will disappear.

IMPORTANT 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. The rear SAM control unit sends the request to display various messages via the interior CAN to the instrument cluster.

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.

IMPORTANT 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 to change to the jump starting mode or the workshop mode and the alternator voltage to be increased to U = 14.3 V.

Electrical function schematic for no-load current management PE54.10-P-2074-97XAA
Electrical function schematic for comfort function shutoff PE54.10-P-2076-97XAA
Overview of energy management system components GF54.10-P-9990FQ