Engine Off Energy Management, Function - GF54.10-P-1050RD
Model 172.4 up to model year 2017
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 chassis CAN (CAN E), 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:
- Consumer shutoff function sequence
- Function sequence for no-load current management
- Function sequence for remote charging/jump start
Additional function requirements for consumer shutoff
- Terminal 15 ON or Terminal 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.
Consumer shutoff function sequence
The rear SAM control unit actuates the consumer shutoff function under the following conditions:
- On-board electrical system voltage lowered to less than U = 11.8 V
- Engine Off
- Change from circuit 15 ON to circuit 15R ON
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 14).
| Shutoff step | Shutoff stage | Consumers with reduced or no power | Executing control unit | Maximum Current in A |
|---|---|---|---|---|
| 1 | 1 | PTC heating level 6, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 2 | 2 | PTC heating level 5, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 3 | 3 | PTC heating level 4, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 4 | 4 | PTC heating level 3, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 5 | 5 | PTC heating level 2, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 6 | 6 | PTC heating level 1, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 7 | 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 |
| 8 | 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 |
| 9 | 10 | Mirror heater | Left door control unit (N69/1) and Right door control unit (N69/2) | 3.5 |
| 10 | 12 | Rear window heater | Rear SAM control unit with fuse and relay module (N10/2) | 30.0 |
| 11 | 14 | Blower P = 50% | ACC control and operating unit (N22/7) | 16.0 |
| 12 | 15 | Combustion engine fan motor P = 50% | ACC control and operating unit (N22/7) | 31.0 |
| 13 | 16 | Circuit 15R relay (1) (SA) | Rear SAM control unit with fuse and relay module (N10/2) | 6.0 |
| 14 | 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 |
| 15 | 19 | Residual heat utilization (with CODE 581 (Automatic air conditioning) and except CODE 494 (USA version)) | ACC control and operating unit (N22/7) | 8.0 |
| 16 | 21 | Telematics, audio | Radio (A2) or COMMAND controller unit (A40/3) | 2.0 |
| MAGIC SKY CONTROL (with CODE 412 (Vario roof in glass version)) | Rear SAM control unit with fuse and relay module (N10/2) | 2.0 |
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 14).
| Shutoff step | Shutoff stage | Consumers with reduced or no power | Executing control unit | Maximum Current in A |
|---|---|---|---|---|
| 1 | 1 | PTC heating level 6, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 2 | 2 | PTC heating level 5, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 3 | 3 | PTC heating level 4, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 4 | 4 | PTC heating level 3, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 5 | 5 | PTC heating level 2, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 6 | 6 | PTC heating level 1, heat boosting (with engine 651.9) | ACC control and operating unit (N22/7) | 18.5 |
| 7 | 8 | Blower P = 50% | ACC control and operating unit (N22/7) | 16.0 |
| 8 | 9 | Combustion engine fan motor P = 50% | ACC control and operating unit (N22/7) | 31.0 |
| 9 | 11 | Circuit 15R relay (1) (SA) | Rear SAM control unit with fuse and relay module (N10/2) | 6.0 |
| 10 | 13 | 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 |
| 11 | 14 | Rear window heater | Rear SAM control unit with fuse and relay module (N10/2) | 30.0 |
| 12 | 16 | 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 |
| 13 | 17 | 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 |
| 14 | 20 | Mirror heater | Left door control unit (N69/1) and Right door control unit (N69/2) | 3.5 |
| 15 | 21 | Residual heat utilization (with CODE 581 (Automatic air conditioning) and except CODE 494 (USA version)) | ACC control and operating unit (N22/7) | 8.0 |
| 16 | 22 | Convenience lighting, interior illumination | Front SAM control unit with fuse and relay module (N10/1) | 1.0 |
| Luggage compartment illumination | Rear SAM control unit with fuse and relay module (N10/2) | 0.5 | ||
| 17 | 25 | Telematics, audio | Radio (A2) or COMMAND controller unit (A40/3) | 2.0 |
| MAGIC SKY CONTROL (with CODE 412 (Vario roof in glass version)) | Rear SAM control unit with fuse and relay module (N10/2) | 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 not activated again until a reset is performed by turning the transmitter key (A8/1) to the circuit 15C ON position.
Additional function requirements for no-load current management
- Transition from terminal 15R to terminal 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 management relay (F32k2) shuts off 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, music 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 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.
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 terminal 15R to terminal 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).
T = 5 min. before opening the no-load current shutoff relay the rear SAM control unit sends a cutoff signal as advance notice to all the control units supplied with power through circuit 30g.
The front SAM control unit sends this cutoff signal over the chassis CAN to the control units connected to the chassis CAN.
The following control units receive the shutoff signal via the interior CAN:
- Instrument cluster (A1)
- Radio (A2) (with code 523 (Audio 20 CD) or code 510 (Audio 20 CD with 6-disk CD-changer))
- COMMAND controller unit (A40/3) (with CODE 527 (COMMAND APS with single DVD drive (with navigation)) or CODE 512 (COMMAND APS with DVD changer))
- Front SAM control unit
- ACC control and operating unit (N22/7)
- Driver seat control unit (N32/1) (with CODE 275 (Memory package))
- Front passenger seat control unit (N32/2) (with CODE 275 (Memory package))
- Vario roof control control unit (N52)
- Left door control unit (N69/1)
- Right door control unit (N69/2)
- KEYLESS-GO control unit (N69/5) (with CODE 889 (KEYLESS-GO))
- Electronic ignition switch control unit
The following control units receive the shutoff signal over the chassis CAN:
- Left reversible emergency tensioning retractor (A76) (with CODE 299 (PRE-SAFE® system))
- Right reversible emergency tensioning retractor (A76/1) (with CODE 299 (PRE-SAFE® system))
- Supplemental Restraint System control unit (N2/10)
- CDI control unit or ME-SFI control unit
- Parking system control unit (N62) (with CODE 230 (Exclusive parking assist))
- Steering column tube module control unit (N80)
- Tire pressure monitor control unit (N88) (with CODE 475 (Tire pressure monitor))
If the interior CAN and chassis CAN are in "sleep mode" during signal transmission, the corresponding control units will be 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. The front SAM control unit receives it and sends it over the chassis CAN to the control units connected to the chassis 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 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 over the chassis CAN to the control units connected to the chassis CAN.
Closing the no-load current shutoff relay causes power to again be supplied via terminal 30g.
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.
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
- Terminal 15R OFF
Function sequence for activating no-load current diagnosis
The battery sensor starts the no-load current diagnosis via the onboard 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 are updated if there are significant changes or if the no-load current diagnosis is canceled.
- 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.
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
Additional function requirements for canceling/ending no-load current diagnosis
- Circuit 15R ON
- On-board electrical system voltage values fall below limits
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 fault roll.
Additional function requirements for no-load current reference value/residual charging current assessment
- Terminal 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 circuit 15 ON.
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 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 instrument cluster's travel distance display or the multifunction display, 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.
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-2074-97TAA | ||
| Electrical function schematic for comfort function shutoff | PE54.10-P-2076-97TAA | ||
| Overview of energy management system components | GF54.10-P-9990RD |