Engine Off Energy Management, Function - GF54.10-P-1050RR
Model 190
Function requirements, general
- "Engine running" or "Drive train operational" signal not set (vehicle switched off)
The ME-SFI control unit (N3/10) sends the "engine running" or "drivetrain operational" signal via the drive train CAN (CAN C1), powertrain control unit (N127), 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 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 (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 permissible discharge current of the on-board electrical system battery is exceeded, the rear SAM control unit activates the consumer reduction function (deactivation of convenience functions) and sends the request for reducing output or shutoff of consumers via the interior CAN to the corresponding control units that are connected to the interior CAN, via the interior CAN, front SAM control unit and chassis CAN 1 to the powertrain control unit and via the interior CAN, AMG gateway control unit (N93/9) and user interface CAN (CAN HMI) to the head unit (A26/17).
The state of the on-board electrical system battery is determined by the electronics integrated in the on-board electrical system battery. The electronics in the on-board electrical system battery send corresponding parameters of the onboard electrical system battery via the battery sensor LIN (LIN B15) 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 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 18).
| Shutoff step | Shutoff stage | Power-reduced or deactivated function | Executing control unit | Maximum current in A |
|---|---|---|---|---|
| 1 | 7 | Seat heater stage 3 (with code 873 (Seat heater for driver and front passenger)) | Rear SAM control unit with fuse and relay module (N10/2) | 13, 2 |
| 2 | 8 | Seat heater stage 2 (with CODE 873 (Seat heater for driver and front passenger)) | Rear SAM control unit with fuse and relay module (N10/2) | 13, 2 |
| 3 | 10 | Mirror heater | Left door control unit (N69/1) and right door control unit (N69/2) | 3, 5 |
| 4 | 12 | Rear window heater | Rear SAM control unit with fuse and relay module (N10/2) | 30, 0 |
| 5 | 14 | Blower P = 50 % | Climate control control unit (N22/1) | 16, 0 |
| 6 | 15 | Fan P = 50% | Powertrain control unit (N127) | 31, 0 |
| 7 | 16 | Circuit 15R relay (1) (N10/2kB) | Rear SAM control unit with fuse and relay module (N10/2) | 6, 0 |
| 8 | 18 | Seat heater stage 1 (with CODE 873 (Seat heater for driver and front passenger)) | Rear SAM control unit with fuse and relay module (N10/2) | 3.3 |
| 9 | 21 | Audio system | Head unit (A26/17) | 2, 0 |
The reduction of output or the deactivation of consumers is not canceled even if the discharge current drops below the permissible level again. Reduction of output or shutoff of consumers is only canceled 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 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 pre-fuse box (F32) shuts off the consumers that are supplied with power 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.
Following a period of t = 6 h, or as soon as certain limits for the on-board electrical system voltage or for the charge level of the on-board electrical system battery are underranged and compromise the engine's starting capability, the energy management initiates the following actions:
- Activation of no-load current management over CAN
- Open no-load current shutoff relay
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.
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 determined by the electronics in the on-board electrical system battery. 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 electronics in the on-board electrical system battery via the battery sensor LIN and evaluates this data. If the on-board electrical system voltage drops to U < 11 V within the waiting time or the permissible discharge current of the on-board electrical system battery is exceeded within the waiting time, the no-load current shutoff relay is opened prematurely.
The electronics in the on-board electrical system battery go into sleep mode depending on the current.
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:
- Front SAM control unit
- Climate control control unit (N22/1)
- AIRSCARF control unit (N25/7) (with code 403 (AIRSCARF system)) Model 190.4
- Driver seat control unit (N32/1) (with CODE P64 (Memory package))
- Front passenger seat control unit (N32/2) (with CODE P64 (Memory package))
- Control unit for vario roof control (N52) Model 190.4
- Left door control unit (N69/1)
- Right door control unit (N69/2)
- KEYLESS-GO control unit (N69/5)
- AMG gateway control unit
The AMG gateway control unit sends the shutoff signal to the following control units via the drive train CAN:
- Dual clutch transmission control unit (N15/13)
- Fuel system control unit (N118)
- DIRECT SELECT INTERFACE (N150)
The AMG gateway control unit sends the shutoff signal to the following control units via the user interface CAN:
- Instrument cluster (A1)
- Head unit
- Reversing camera (B84/3) (with CODE 218 (Reversing camera))
- Tire pressure monitor control unit (N88) (with CODE 475 (Tire pressure monitor))
The head 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:
- Audio/COMAND display (A40/8)
- Audio/COMAND control panel (A40/9)
- Touchpad (A105) (with CODE 531 (COMAND APS))
The head unit sends the shutoff signal via MOST to the sound system amplifier control unit (N40/3) (with CODE 810 (Sound system)) or to the Advanced sound system amplifier control unit (N40/7) (with CODE 811 (Advanced sound system)).
The front SAM control unit sends the shutoff signal via chassis CAN 1 to the following control units:
- Supplemental Restraint System control unit (N2/10)
- ME-SFI [ME] control unit
- Drivetrain control unit
- Electric parking brake control unit (N128)
The front SAM control unit sends the shutoff signal via chassis CAN 2 (CAN E2) to the following control units:
- Multifunction camera (A40/11) (with CODE 22P (Lane package), CODE 513 (Traffic sign recognition) or CODE 608 (Adaptive Highbeam Assist))
- Left headlamp control unit (E1n9)
- Right headlamp control unit (E2n9)
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.
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 not opened again until the waiting time of t = 6 h has expired or the permissible discharge current of the on-board electrical system battery is exceeded. 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 activities will trigger the closure of the no-load current shutoff relay:
- Switching on terminal 15R
- Unlocking or opening of a door or the liftgate or switching on circuit 15C
- Switching on hazard warning system, standing or parking lights
- Activation of the 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))
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 circuit 15 status over the interior CAN to the rear SAM control unit.
Function sequence for activating no-load current diagnosis
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.
- Limit for the 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 (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 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
- Limit for the discharge current of the on-board electrical system battery has been exceeded
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 voltage diagnosis is aborted if the limit for the discharge current of the on-board electrical system battery is exceeded. The electronics in the onboard electrical system battery will discontinue no-load current monitoring in order to minimize power consumption. Once this happens, no further entries will be added to the 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. 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, AMG gateway control unit and user interface CAN to the instrument cluster. The minimum no-load current occurring since locking is determined and stored by the electronics in the on-board electrical system battery.
After the vehicle is woken up, the electronics in the on-board electrical system battery send the measured no-load current value via 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.
If the measured no-load current is within a defined tolerance range, the message in the multifunction display of the instrument cluster disappears.
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. The rear SAM control unit sends the request to display various messages via the interior CAN, AMG gateway control unit and user interface 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.
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. 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-2074-97HBA | ||
| Electrical function schematic for comfort function shutoff | PE54.10-P-2076-97HBA | ||
| Overview of energy management system components | GF54.10-P-9990RR |