Engine off energy management, function - GF54.10-P-1050RF
Model 205, 253
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 "drivetrain operational" signal via the drive train CAN (CAN C1), powertrain control unit (N127), chassis 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 no-load current management
- 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 circuit 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 for t = 5 s falls to below U = 11.8 V, the front SAM control unit activates the consumption reduction function (shutoff comfort functions) and sends the request to reduce output or shut off consumers to the appropriate control units that are connected to the interior CAN via interior CAN, electronic ignition lock control unit, chassis FlexRay, powertrain control unit and drive train CAN to the CDI control unit or the ME-SFI control unit and via interior CAN, electronic ignition lock control unit and user interface CAN (CAN HMI) to the head unit (A26/17).
Model 205.012/047/147/212/247
The energy requirement of the active consumers is 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.
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 cut off out of the engine ON energy management function (up to shutoff stage 20).
| Sequence | Shutoff stage | Consumers with reduced or no power | Responsible control unit |
|---|---|---|---|
| 1 | 1 | PTC 1st branch, heat boosting (engine 626, 651) | Climate control unit (N22/1) |
| 2 | 2 | PTC 2nd branch, heat boosting (engine 626, 651) | Climate control unit (N22/1) |
| 3 | 3 | PTC 3rd branch, heat boosting (engine 626, 651) | Climate control unit (N22/1) |
| 4 | 4 | PTC 4th branch, heat boosting (engine 626, 651) | Climate control unit (N22/1) |
| 5 | 5 | PTC 5th branch, heat boosting (engine 626, 651) | Climate control unit (N22/1) |
| 6 | 6 | PTC 6th branch, heat boosting (engine 626, 651) | Climate control unit (N22/1) |
| 7 | 9 | Spray nozzle hose heater (with CODE 875 (Heated windshield washer system)) | Front SAM control unit (N10/6) |
| 8 | 10 | Mirror heater | Left front door control unit (N69/1) and right front door control unit (N69/2) |
| 9 | 11 | Seat heater stage 3 (with CODE 401 (Seat climate control for driver and front passenger) or CODE 873 (Seat heater for driver and front passenger)) | Rear SAM control unit (N10/8) |
| 10 | 12 | Rear window heater | Rear SAM control unit (N10/8) |
| 11 | 14 | Seat heater stage 2 (with CODE 401 (Seat climate control for driver and front passenger) or CODE 873 (Seat heater for driver and front passenger)) | Rear SAM control unit (N10/8) |
| 12 | 15 | Rear blower P = 50 % (with CODE 581 (Automatic air conditioning)) | Climate control unit (N22/1) |
| 13 | 16 | Blower in front P = 50% | Climate control unit (N22/1) |
| 14 | 17 | Fan P = 50% | CDI control unit (N3/9) (diesel engine) or ME-SFI control unit (N3/10) (gasoline engine) |
| 15 | 18 | Trunk socket, cigarette lighter (with CODE 301 Smoker's package) | Front SAM control unit (N10/6) |
| 16 | 20 | Seat heater stage 1 (with CODE 401 (Seat climate control for driver and front passenger) or CODE 873 (Seat heater for driver and front passenger)) | Rear SAM control unit (N10/8) |
| 17 | 20 | Seat ventilation (with CODE 401 (Seat climate control for driver and front passenger)) | Rear SAM control unit (N10/8) |
| 18 | 21 | Residual heat utilization (with CODE 581 (Automatic air conditioning) or CODE 965 (Taxi/rental car preinstallation)) | Climate control unit (N22/1) |
| 19 | 22 | Rear blower P = 0 % (with CODE 581 (Automatic air conditioning)) | Climate control unit (N22/1) |
| 20 | 23 | Stationary heater (with CODE 228 (Stationary heater)) | Climate control unit (N22/1) |
| 21 | 24 | Telematics, audio, telephone, GPS | Head unit (A26/17) |
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 enabled again after engine start.
Additional function requirements for no-load current management
- Transition from circuit 15R to circuit 15C
The electronic ignition lock control unit sends the status of circuit 15 to the front SAM control unit over the interior CAN.
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 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 circuit 30g.
No-load current management however, can accommodate increased power consumption for a specific period after switching off the engine (maximum t = 75 min.). This allows, for example, the radio to be played while the car is being washed. No-load current management cyclically measures the voltage and power consumption every t = 6 minutes. If an excessively high no-load current is determined for a specific period, the no-load current management relay is opened at the earliest after t = 75 min., but no later than t = 6 h.
After t = 6 h elapses or as soon as the limit value for on-board electrical system voltage (except CODE U98 (LITHIUM-ION STARTER BATTERY (LISB))) or for the charge level of the on-board electrical system battery (with CODE U98 (LITHIUM-ION STARTER BATTERY (LISB))) is dropped below and the ability to start the engine is thus jeopardized, 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 interior CAN. This signal also causes, for example, 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 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 function 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 recorded by the battery sensor (B95) (except CODE U98 (LITHIUM-ION STARTER BATTERY (LISB))) or by the electronics in the on-board electrical system battery (with CODE U98 (LITHIUM-ION STARTER BATTERY (LISB))). 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 electronics in the on-board electrical system battery via battery sensor LIN (LIN B15) and evaluates it. If the on-board electrical system voltage drops within the waiting time to U < 11 V or the permissible discharge current of the on-board electrical system battery is exceeded, the no-load current shutoff relay is opened prematurely.
If U < 11 V, the battery sensor will go into sleep mode (reduced power consumption).
The electronics in the on-board electrical system battery go into sleep mode (reduced power consumption) depending on the current.
The front SAM control unit sends a shutoff signal t = 5 minutes before opening the no-load current shutoff relay as advance notice over 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:
- Panoramic sliding sunroof control unit (with CODE 413 (Panoramic sliding sunroof))
- Sliding roof control module (A98/1) (with CODE 414 (Sliding roof))
- Climate control unit (N22/1)
- Trailer recognition control unit (N28/1) (with CODE 550 (Trailer hitch))
- Driver seat control unit (N32/1) (with CODE 275 (Memory package))
- Front passenger seat control unit (N32/2) (with CODE 242 (Electrically adjustable front passenger seat with memory function))
- Camera cover control unit (N42) (with CODE 218 (Reversing camera) or CODE 501 (360° camera))
- Electronic ignition switch control unit
- Trunk lid control unit (N121) (with CODE 881 (Remote trunk closing))
- Liftgate control unit (N121/1) (with CODE 890 (EASY-PACK liftgate))
The electronic ignition lock control unit sends the shutoff signal over the chassis FlexRay to the following control units:
- Stereo multifunction camera (A40/13) (with CODE 23P (Driving assistance package Plus))
- AIRmatic control unit (N51/3) (model 205 with CODE 483 (ADVANCED AGILITY package) and CODE 489 (AIRmatic))
- AIR BODY CONTROL unit (N51/3) (model 253 with CODE 489 (AIR BODY CONTROL))
- Parking system control unit (N62) (with CODE 235 (Active Parking Assist))
- Radar sensors control unit (N62/1) (with CODE 23P (Driving assistance package Plus))
- Steering column tube module control unit (N80)
The electronic ignition lock control unit sends the shutoff signal over the user interface CAN to the following control units:
- Head unit (A26/17)
- Head-up display (A40/12) (with CODE 463 (Head-up display))
- Left front reversible emergency tensioning retractor (A76) (with CODE 299 (PRE-SAFE® system))
- Right front reversible emergency tensioning retractor (A76/1) (with CODE 299 (PRE-SAFE® system))
- Reversing camera (B84/3) (with CODE 218 (Reversing camera))
- Tire pressure monitor control unit (N88) (with CODE 475 (Tire pressure monitor))
- 360° camera control unit (N148) (with CODE 501 (360° camera))
The electronic ignition lock control unit sends the shutoff signal via the periphery CAN (CAN PER) to the following control units:
- Mono multifunction camera (A40/11) (with CODE 640 (High-performance LED) or CODE 641 (DYNAMIC LED HEADLAMPS (LEFT-HAND TRAFFIC)) or CODE 642 (DYNAMIC LED HEADLAMPS (RIGHT-HAND TRAFFIC)) and CODE 22P (Lane package))
- Left headlamp control unit (E1n9) (with CODE 631 (Static LED headlamps (left-hand traffic)) or CODE 632 (Static LED headlamps (right-hand traffic)) or CODE 640 (High-performance LED) or CODE 641 (DYNAMIC LED HEADLAMPS (LEFT-HEAD TRAFFIC)) or CODE 642 (DYNAMIC LED HEADLAMPS (RIGHT-HEAD TRAFFIC)))
- Right headlamp control unit (E2n9) (with CODE 631 (Static LED headlamps (left-hand traffic)) or CODE 632 (Static LED headlamps (right-hand traffic)) or CODE 640 (High-performance LED) or CODE 641 (DYNAMIC LED HEADLAMPS (LEFT-HEAD TRAFFIC)) or CODE 642 (DYNAMIC LED HEADLAMPS (RIGHT-HEAD TRAFFIC)))
- 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) (transmission 722)
The head unit sends the shutoff signal via the telematics CAN (CAN A) to the following control units:
- Audio/COMAND display (A40/8)
- Audio/COMAND control panel (A40/9)
- Touchpad (A105) (with CODE 522 (Audio 20 radio) or CODE 531 (COMAND APS))
The head unit sends the shutoff signal to the following control units via MOST:
- 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))
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 front SAM control unit sends the switching status of the no-load current shutoff relay via interior CAN.
Detailed information on the signal flow is given in the chapter on 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 V or the permissible discharge current of 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 circuit 15R
- Unlocking or opening of a door or the trunk lid (model 205.0/1) or the liftgate (model 205.2, 253) or switching on circuit 15C
- Switching on of the hazard warning system, the standing or parking lights or the signaling system of special-purpose vehicles
- Activation of anti-theft alarm system (with CODE 551 (Anti-theft alarm system (ATA)))
- Triggering of the panic alarm (with CODE 494 (USA version))
- Activation of stationary heater (with CODE 228 (Stationary heater))
Function sequence for no-load current diagnosis
No-load current diagnosis records data to help troubleshoot possible fault profiles.
The no-load current diagnosis function comprises the following subfunctions:
- Function sequence for activating no-load current diagnosis
- Function sequence for terminating/ending no-load current diagnosis
Additional function requirements for activating no-load current
- Circuit 15R OFF
The electronic ignition lock control unit sends the status of circuit 15 to the front SAM control unit over the interior CAN.
Function sequence for activating no-load current diagnosis
The battery sensor or the electronics in the on-board electrical system battery start the no-load current diagnosis via the battery sensor 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 limits are dropped below or permissible discharge current of on-board electrical system battery is exceeded 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. 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 wake-up event of the battery sensor or electronics in the on-board electrical system battery will cause the data record to be updated.
Additional function requirements for canceling/ending no-load current diagnosis
- 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 circuit 15 to the front SAM control unit over the interior CAN.
Function sequence for terminating/ending no-load current diagnosis
The no-load current diagnosis is canceled if the on-board electrical system voltage drops below the limit value (U < 11 V) or the permissible discharge current of the on-board electrical system battery is exceeded. The battery sensor or the electronics 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 memory.
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 IC (A1). The diagnostic tester must then be removed and the vehicle locked so that the vehicle's no-load current will quickly drop. 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 minimum no-load current occurring since locking is determined and stored by the battery sensor or electronics in the on-board electrical system battery. After the vehicle has "woken up", the battery sensor or the electronics 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 multifunction display of the IC goes out.
If the no-load current reference value is too high, a no-load current 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 state of charge 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.
Model 205.012/047/147/212/247
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 (N129/1) measures a voltage of more than U = 12.8 V in the 12 V on-board electrical system, energy with a maximum power of P = 500 W is transferred via 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 circuit 15 ON).
Charge on-board electrical system battery in well-ventilated rooms only.
Turn on charging unit only after connecting it to battery. Turn off charging unit before disconnecting it from battery. Only charge on-board electrical system battery with direct current.
During the jump start procedure or in the workshop during testing work, one of the front doors must be opened to enable the alternator management to switch to jump starting or 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-2074-97FBA | ||
| Electrical function schematic for comfort function shutoff | PE54.10-P-2076-97FBA | ||
| Overview of energy management system components | GF54.10-P-9990RF |