GF54.10-P-2001RIT on-Board Electrical System Emergency Mode, Function
GF54.10-P-2001RIT On-board Electrical System Emergency Mode, Function
- with CODE (P99) Special model "AMG Black Series"
General function requirements
^ Circuit 61 ON
The status of circuit 61 is placed on the interior CAN (CAN B) by the passenger-side SAM control unit (N10/11).
On-board electrical system emergency mode, general
The vehicle power supply control unit (N82/1) controls the on unit board electrical system emergency mode in relation to the voltage of the on-board electrical system battery (G1).
If the voltage drops below U ≤= 10.8 V for t ≥= 10 s, the vehicle power supply control unit activates on-board electrical system emergency mode and sends a corresponding signal to the interior CAN.
On-board electrical system emergency mode consists of the following subfunctions:
^ Idle speed increase function sequence
^ Consumer shutoff function sequence
Idle speed increase function sequence
The vehicle power supply control unit transmits the request "Increase idle speed" via the interior CAN to the EIS [EZS] control on unit (N73), which forwards it via the engine compartment CAN to the ME-SFI [ME] control unit (N3/10). The ME-SFI [ME] control unit receives the request and increases the idle speed, but only after the engine has reached a rated speed of n > 900 rpm. The increased idle speed increases the power output of the alternator (G2).
The idle speed increase is revoked when:
- Engine off or alternator defective
- Simultaneous occurrence of the following conditions:
- Consumer shutoff not activated
- On-board electrical system emergency mode not active
Consumer shutoff function sequence
As soon as the alternator is no longer able to provide the requested electrical output, the consumer shutoff function is activated. The consumer shutoff function is also referred to as dynamic load management.
The on-board electrical load is reduced by cutting back convenience functions. This avoids a negative charge balance and ensures that starting ability is preserved.
The consumer shutoff function is canceled when the alternator is again able to provide the requested electrical output to stabilize the on-board electrical system voltage.
Consumer shutoff is subdivided into the following two stages:
- Shutoff stage 1: U < 10.6 V at the on-board electrical system battery
- Shutoff stage 2: U < 10.2 V at the on-board electrical system battery
In shutoff stage 1, the following functions are shut off depending on the vehicle equipment:
- Wiper park position heater (R2/10)
- Steering column tube adjustment
- Heated rear window (R1)
- Interior illumination
- Ventilation control of air conditioning system
The following components are actuated at reduced power output:
- Blower motor (A32m1) with P < 69 %
- Telematics (current limited to I = 11 A)
Corresponding fault messages are issued by the battery symbol lighting up in the left multifunction display (A1p13) and by display of the text "Electrical consumers shut off." in the right multifunction display (A1p15).
The following consumers are additionally switched off during shutoff stage 2:
- Mirror heater (M21/1r1 and M21/2r1)
- Inside rearview mirror unit (A67)
The following component is actuated at reduced power output in shutoff stage 2:
- Blower motor with P < 53 %
The fault messages in the multifunction displays remain the same.
On-board electrical system emergency mode is deactivated under the following conditions:
- Battery voltage U > 11.8 V for t >= 10 s
- Transition from circuit 15R to circuit 15C
The idle speed increase is reset by the vehicle power supply control unit, but the idle speed is actually reduced only after the engine is restarted.
The consumers shut down are reactivated during the next ignition sequence (after circuit 15R ON).
The circuit status of circuit 15 is made available by the EIS [EZS] control unit on the interior CAN.
