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

MODEL 166 up to model year 2016 

Function requirements, general 

IMPORTANT The CDI control unit (N3/9) (diesel engine) or the ME-SFI [ME] control unit (N3/10) (gasoline engine) sends the "Engine running" or the "Drive train operational" signal over the chassis CAN 1 (CAN E1), electronic ignition lock control unit (N73) and the interior CAN (CAN B) to the SAM control unit (N10).

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 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:

Additional function requirements for consumer shutoff 

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

Consumer shutoff function sequence 

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

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.

IMPORTANT The list includes those consumers whose power supply is reduced or cut off out of the engine ON energy management function (up to shutoff stage 18).

Sequence Shutoff stage Consumers with reduced or no power Responsible control unit Maximum Currentin A
1 1 Heating level 6, heat boosting (engine 642.8, 651.9), passenger side (83_%) Automatic climate control and operating unit (N22/7) 18.5
2 2 Heating level 5, heat boosting (engine 642.8, 651.9), driver side Automatic climate control and operating unit (N22/7) 18.5
3 3 Heating level 4, heat boosting (engine 642.8, 651.9), passenger side Automatic climate control and operating unit (N22/7) 18.5
4 4 Heating level 3, heat boosting (engine 642.8, 651.9), driver side Automatic climate control and operating unit (N22/7) 18.5
5 5 Heating level 2, heat boosting (engine 642.8, 651.9), passenger side Automatic climate control and operating unit (N22/7) 18.5
6 6 Heating level 1, heat boosting (engine 642.8, 651.9), driver side Automatic climate control and operating unit (N22/7) 18.5
7 7 Seat heater level 3 (with CODE 401 (Front comfort seats, incl. seat heating and seat ventilation) or with CODE 873 (Seat heater for front seat at left and right)) Driver seat control unit (N32/1) and front passenger seat control unit (N32/2) 13.2
8 8 Seat heater level 2 (with CODE 401 (Front comfort seats, incl. seat heating and seat ventilation) or with CODE 873 (Seat heater for front seat at left and right)) Driver seat control unit (N32/1) and front passenger seat control unit (N32/2) 13.2
9 9 Wiper park heater Automatic climate control and operating unit (N22/7) 15, 0
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 Automatic climate control and operating unit (N22/7) 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 Sockets SAM control unit (N10) 6.0 - 8.0
17 18 Seat heater level 1 (with CODE 401 (Front comfort seats, incl. seat heating and seat ventilation) or with CODE 873 (Seat heater for front seat at left and right)) Driver seat control unit (N32/1) and front passenger seat control unit (N32/2) 3.3
18 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
    Rear blower (with CODE 581 (Comfort automatic air conditioning)) P = 0 % Automatic climate control and operating unit (N22/7) 6.0
19 20 Stationary heater (with CODE 228 (Stationary heater)) Stationary heater control unit (A6n1) 10.0
20 21 Telematics, audio, telephone Radio (A2) (with CODE 523 (MB Audio 20 radio) or CODE 510 (Audio 20 incl. CD changer)) or COMAND controller unit (A40/3) (with CODE 527 (COMAND APS with single DVD drive (with navigation)) or CODE 512 (COMAND APS incl. DVD changer) or CODE 528 (COMAND incl. DVD changer)) 2, 0

Even when the on-board electrical system voltage stabilizes at a value in excess of U = 11.8 V, the consumer shutoff is not canceled. The switched-off consumers are switched on again only after Circuit 15C ON has been reset.

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 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 SAM control unit. Actuation of the circuit 30g relay (F33k1) switches off the 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 circuit 30g relay is opened at the earliest after t = 75 minutes, but no later than after t = 6 hours.

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:

Before the circuit 30g relay is opened a corresponding signal to reduce the power of the control units is transmitted via CAN. This prompts, for example, the sliding roof control module (A98/1) (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 

No-load current management encompasses 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 monitored by the battery sensor (B95). If the no-load current is too high, the circuit 30g relay will be opened after t = 75 min. The SAM control unit reads in the data from the battery sensor over the battery sensor-LIN (LIN B15) and evaluates it.

If the on-board electrical system voltage drops within the waiting time to U < 11.8 V, the circuit 30g relay is prematurely opened.

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

At t = 5 min. before the circuit 30g relay is opened, the SAM control unit sends a shutoff signal over the interior CAN as advance notice to the control units involved. 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 electronic ignition lock control unit sends the shutoff signal over the chassis CAN 1 to the following control units:

The electronic ignition lock control unit sends the shutoff signal over the chassis CAN 2 (CAN E2) to the following control units:

If the interior CAN, chassis CAN 1 and chassis CAN 2 are in the "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 

After expiry of t = 5 min. the no-load current management opens the circuit 30g relay, provided there has been no reason to shut down in the meantime. The SAM control unit sends the circuit 30g relay status over the interior CAN and the electronic ignition lock control unit over chassis CAN 1 and chassis CAN 2 to the corresponding control units.

Function sequence for energize consumers 

The no-load current management closes the circuit 30g relay as soon as a system is activated. All the functions are then available again. The circuit 30g 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 SAM control unit receives a wake-up signal, the no-load current management closes the circuit 30g relay and signals over the interior CAN that the wake-up conditions for the control units are active again. The electronic ignition lock control unit receives this signal and sends it over chassis CAN 1 and chassis CAN 2 to the corresponding control units. Closing the circuit 30g relay causes power to again be supplied via circuit 30g.

The following conditions authorize a closing of the circuit 30g relay:

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:

Additional function requirements for activating no-load current 

Function sequence for activating no-load current diagnosis 

The battery sensor starts the no-load current diagnosis via the battery sensor 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. 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:

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 

Function sequence for terminating/ending no-load current diagnosis 

The no-load current diagnosis is canceled when the limit value (U < 11.8 V) for the on-board electrical system voltage is undershot. The battery sensor will discontinue no-load current monitoring in order to minimize electricity consumption. Once this happens, no further data will be added to the no-load current fault roll.

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

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 evaluation function comprises the following subfunctions:

Function sequence for measuring no-load current-reference value 

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 over the battery sensor LIN to the rear 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.

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

IMPORTANT Charge on-board electrical system battery in well-ventilated rooms only. Turn on charging unit after connecting it to battery. Turn off charging unit before disconnecting it from battery. Charge on-board electrical system battery with DC only, a charging current of approx. 10 % of the capacity is recommended for the charging process.

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 = 13.9 V.

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