Engine off energy management, function - GF54.10-P-1050CAM
MODEL 207.3/4 as of model year 2014
Function requirements, general
- "Engine running" or "Drivetrain operational" signal not set (engine switched off)
The CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) sends the "Engine running" or "Drivetrain operational" signal via chassis CAN 1 (CAN E1), 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 engine when the vehicle is parked.
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 electrical consumers may be switched off.
Engine OFF energy management encompasses the following subfunctions:
- Function sequence for consumer reduction (deactivation of convenience functions)
- Function sequence for no-load current management
- Function sequence for remote charging/jump start
Additional function requirements for consumer reduction (deactivation of comfort functions)
- 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.
Function sequence for consumer reduction (deactivation of convenience functions)
If the on-board electrical system voltage drops below U = 11.8 V for t = 5 s, the rear SAM control unit activates the consumer reduction function (deactivation of comfort functions) and sends the request to reduce the power consumption of consumers or to deactivate consumers via the interior CAN to the corresponding control units.
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 step 15).
| Shutoff step | Shutoff stage | Power-reduced or deactivated function | Executing control unit | Maximum current in A |
|---|---|---|---|---|
| 1 | 1 | Heating level 6, heat boosting (with engine 642.8, 651.9), passenger side | Automatic climate control and operating unit (N22/7) | 18.5 |
| 2 | 2 | Heating level 5, heat boosting (with engine 642.8, 651.9), driver side | Automatic climate control and operating unit (N22/7) | 18.5 |
| 3 | 3 | Heating level 4, heat boosting (with engine 642.8, 651.9), passenger side | Automatic climate control and operating unit (N22/7) | 18.5 |
| 4 | 4 | Heating level 3, heat boosting (with engine 642.8, 651.9), driver side | Automatic climate control and operating unit (N22/7) | 18.5 |
| 5 | 5 | Heating level 2, heat boosting (with engine 642.8, 651.9), passenger side | Automatic climate control and operating unit (N22/7) | 18.5 |
| 6 | 6 | Heating level 1, heat boosting (with engine 642.8, 651.9), driver side | Automatic climate control and operating unit (N22/7) | 18.5 |
| 7 | 7 | Seat heater stage 3 (with CODE 401 (Front comfort seats, incl. seat heating and seat ventilation) or CODE 873 (Seat heater for left and right heated front seat)) | Rear SAM control unit with fuse and relay module (N10/2) | 13.2 |
| 8 | 8 | Seat heater stage 2 (with CODE 401 (Front comfort seats, incl. seat heating and seat ventilation) or CODE 873 (Seat heater for left and right heated front seat)) | 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 | 14 | Blower P = 50 % | Automatic climate control and operating unit (N22/7) | 16.0 |
| 13 | 15 | Fan P = 50% | Automatic climate control and operating unit (N22/7) | 31.0 |
| 14 | 16 | Circuit 15R relay (1) (N10/2kB) | Rear SAM control unit with fuse and relay module (N10/2) | 6.0 |
| 15 | 18 | Seat heater stage 1 (with CODE 401 (Front comfort seats, incl. seat heating and seat ventilation) or CODE 873 (Seat heater for left and right heated front seat)) | Rear SAM control unit with fuse and relay module (N10/2) | 3.3 |
| 16 | 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) | 8.0 |
| 17 | 20 | Stationary heater (with CODE 228 (Stationary heater)) | Stationary heater control unit (A6n1) | 10.0 |
| 18 | 21 | Audio system | Radio (A2) (with CODE 523 (MB Audio 20 radio) or CODE 510 (Audio 20 with CD changer)) 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)) | 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 ON has been reset.
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 shutoff relay (F32k2) in the front prefuse box (F32) shuts off consumers that are supplied with power via 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 shutoff 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's voltage values drop below certain limits and compromise the engine's starting capability, the extended run-on monitoring function initiates the following actions:
- 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 causes, for example, the panoramic sliding sunroof control unit (A98n1) (with CODE 413 (Panoramic glass sunroof with top sliding sunroof)) to move an open panoramic sliding sunroof to the tilt position.
The no-load current management system comprises 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
The no-load current shutoff system comprises 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).
At t = 5 min before the no-load current shutoff relay is opened, the rear SAM control unit sends a shutoff signal as advance notice to all control units supplied with power via circuit 30g. The rear SAM control unit transmits this cutoff signal via interior CAN.
The following control units receive the shutoff signal via the interior CAN:
- Radio (A2) (with CODE 523 (MB Audio 20 radio) or CODE 510 (Audio 20 with CD changer)) 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))
- Panoramic sliding sunroof control unit (with code (413) Panoramic glass sunroof with top sliding sunroof)
- Front SAM control unit
- Rear control unit (N22/6)
- Automatic climate control and operating unit (N22/7)
- AIRSCARF system control unit (N25/7) (with CODE 403 (AIRSCARF system))
- Trailer recognition control unit (N28/1) (for CODE 550 (Trailer hitch))
- Driver seat control unit (N32/1) (with CODE 275 (Memory package (driver seat, steering column, mirrors)))
- Front passenger seat control unit (N32/2) (with CODE 242 (Electrically adjustable front passenger seat with memory))
- Camera cover control unit (N42) (with CODE 218 (Reversing camera) or CODE 501 (360-degree camera))
- Left front door control unit (N69/1)
- Right front door control unit (N69/2)
The radio or the COMAND controller unit sends the shutoff signal via the telematics CAN (CAN A) and Media Oriented System Transport (MOST).
The following control units receive the shutoff signal via the telematics CAN:
- Navigation module (A2/30) (with CODE 509 (Navigation box)) in holder for navigation module (A2/30-1) (with CODE 508 (Navigation box preinstallation))
- Audio/COMAND display (A40/8)
- Audio/COMAND control panel (A40/9)
The following control units receive the shutoff signal via MOST:
- TV digital tuner (A90/3) (with CODE 865 (TV tuner))
- Sound system amplifier control unit (N40/3) (with CODE 810 (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 the shutoff 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 [ME] control unit
- Steering column tube module control unit (N80)
The following control units receive the shutoff signal over chassis CAN 2:
- Multifunction camera (A40/11) (with CODE 608 (Adaptive Highbeam Assist) or CODE 628 (AUTOMATIC HIGH BEAM CONTROL PLUS (IHC+)) and CODE 513 (Speed Limit Assist) and CODE 23P (Driving assistance package))
- Reversing camera (B84/3) (with CODE 218 (Reversing camera))
- Left headlamp control unit (E1n9)
- Right headlamp control unit (E2n9)
- Parking system control unit (N62) (with CODE 235 (Active Parking Assist))
- Tire pressure monitor control unit (N88) (with CODE 475 (Tire pressure monitor (premium)), Schrader)
- 360° camera control unit (N148) (with CODE 501 (360 degree camera))
- Chassis gateway control unit (N93/7) (with CODE 23P (Driving assistance package PLUS))
The chassis gateway control unit sends this shutoff signal via the chassis FlexRay (Flex E).
The following control units receive the shutoff signal via the chassis FlexRay:
- Stereo multifunction camera (A40/13) (with CODE 608 (Adaptive Highbeam Assist) or CODE 628 (AUTOMATIC HIGH BEAM CONTROL PLUS (IHC+)) and CODE 513 (Speed Limit Assist) and CODE 23P (Driving assistance package))
- Radar sensors control unit (N62/1) (for code 23P (Driving assistance package PLUS))
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. For this purpose, the rear SAM control unit actuates the no-load current shutoff relay directly. The rear SAM control unit then sends the switching status of the no-load current shutoff relay via the interior CAN to the corresponding control units.
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. 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 conditions will trigger the closure of the no-load current shutoff relay:
- Switching on circuit 15R:
The timer for the waiting time is reset. The no-load current shutoff relay remains closed as long as the status of circuit 15R is ON.
- Unlocking or opening of a door or switching on circuit 15C:
The timer for the waiting time is reset.
- Switching on of the hazard warning system, the standing or parking lights or the signaling system of special-purpose vehicles:
The timer for the waiting time is reset.
- Activation of anti-theft alarm system (ATA) (with CODE 551 (Anti-theft alarm system (ATA))):
The timer for the waiting time is reset.
- Triggering of panic alarm (with CODE 763 (Radio remote control with panic switch)):
The timer for the waiting time is reset.
- Activation of stationary heater (with CODE 228 (Stationary heater)):
The timer for the waiting time is reset.
Function sequence for no-load current diagnosis
No-load current diagnosis records data to help troubleshoot possible fault profiles.
The no-load current diagnosis comprises the following subfunctions:
- Function sequence for activate no-load current diagnosis
- Function sequence for cancel/end no-load current diagnosis
Additional function requirements for Activate no-load current diagnosis
- Circuit 15R OFF
Function sequence for activate no-load current diagnosis
The battery sensor starts the no-load current diagnosis over 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 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 will cause the data record to be updated.
Additional function requirements for cancel/end no-load current diagnosis
- Circuit 15R ON
- On-board electrical system voltage values exceed limits
Function sequence for cancel/end 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 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 evaluation function comprises 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 (A1). The request for this is sent by the rear SAM control unit via the interior 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 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. The request for this is sent by the rear SAM control unit via the interior CAN to 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 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-2074-97EAB | ||
| Electrical function schematic for comfort function shutoff | PE54.10-P-2076-97EAB | ||
| Overview of energy management system components | GF54.10-P-9990CAM |