Mercedes-Benz E-Class Series 207 Service Manual page 72

The consumer reduction function is canceled as
soon as the alternator is again able to provide the
requested electrical output to stabilize the on-board
electrical system.
A special case of consumer reduction is on-board
electrical system limp-home mode. This is acti-
vated by the on-board electrical system manage-
ment in the rear SAM control unit if the on-board
electrical system voltage drops below U = 10.6 V
for t = 10 s. The following functions of energy
management driving mode are activated:
• Idle speed increase
• Deactivation of alternator management
• Consumer reduction with shutoff of short-term
power consumers
The consumer power reduction or shutoff occurs
with a cycle period of t = 200 ms.
Main components of on-board electrical system, shown on the E 350 CGI
B95 Battery sensor
F32 Front prefuse box
G1 On-board electrical system battery
– This printout will not be recorded by the update service. Status: 01 / 2009 –
On-board electrical system
Dynamic idle speed control
The dynamic rpm increase is intended to adjust the
idle speed of the engine so that no power is drawn
from the on-board electrical system battery while
idling. Accordingly, when consumer load is high, a
high idle speed is set. In contrast to the previous
rpm increase function, which takes effect when the
voltage drops below a given limit or when a certain
consumer shutoff stage is reached, the dynamic
idle speed control is intended to act preventively.
Therefore it does not react to a lack of electrical
energy, but determines in advance the necessary
idle speed for the current load.
The required idle speed increase is computed via
the on-board electrical system control in the rear
SAM control unit and forwarded to the CDI or
ME-SFI control unit. This calculates the idle speed
that is actually required, taking into account various
engine characteristics.
G2
N3/10
N10/2
Introduction of the New E-Class Coupé, Model Series 207
Alternator
ME-SFI [ME] control unit
Rear SAM control unit with fuse and relay
module
P54.10-3191-00
71
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