Power management

Reduction or shutdown of individual current consumers

The power management a subsystem of the energy management. The power management is run from the engine control module (DME or DDE: digital engine electronics or digital diesel electronics). See also functional description or SBT 'Power supply'.

A function of the Advanced Power Management (APM) is the shutdown of individual consumer units or the reduction of power intake. The APM is only implemented in vehicles with the intelligent battery sensor.

System functions

The following system functions are described for power management (”Advanced Power Management”):

Reduction or shutdown of individual current consumers

Reduction or shutdown of individual current consumers

The cutoff of individual consumer units or reduction of the power consumption lowers the power consumption in critical situations. This prevents the battery from discharging.

Important!

When the shutdown of individual consumer units or the reduction of power consumption is activated, the displays remains active (LEDs remain lit).

With the engine running
With the engine running, the shutdown of individual consumer units or reduction in the power consumption is only activated under 2 conditions:

Battery charge state in the critical range
Alternator subjected to full load

The following measures are performed in sequence under the preconditions described:

Function	Operation	Control module (depending on model series and variant)
Rear-window defroster (demister)	Cyclic switching	IHR, IHS, IHKR, IHKS or IHKA
Seat heating	Stage 2	Seat module or JBE
Seat heating	50 %	Seat module or JBE
Active Seat	AUS	Seat module
Heater fan	75 %	IHR, IHS, IHKR, IHKS or IHKA
Heater fan	50 %	IHR, IHS, IHKR, IHKS or IHKA
Mirror heating and washer-nozzle heating	AUS	Door module, KGM, JBE or FRM
Rear-window defroster (demister)	AUS	IHR, IHS, IHKR, IHKS or IHKA
Seat heating	AUS	Seat module or JBE
Active seat ventilation	AUS	Seat module
Heater fan	AUS	IHR, IHS, IHKR, IHKS or IHKA

When the battery charge state moves out of the critical range, the functions are then 100 % available.

With the engine off and ignition switched on
With the engine off and ignition switched on, the shutdown of individual consumer units or reduction in the power consumption is only activated in the following model series and variants:

E81, E82, E87, E90, E91, E92, E93: vehicles with N43 petrol engine and vehicle with N47 diesel engine and manual transmission.
R55, R56: vehicles with manual transmission as of model year 08/2007.

In order to prevent excessive power consumption when the engine is switched off, on these vehicles the seat heating, mirror heating, washer-nozzle heating and heated rear window are switched off and the heater blower is reduced to 75 % power consumption. The displays remain active (LEDs still lit).

Notes for Service department

General information

Note! Procedure in the event of a customer complaint with regard to malfunctions

In the event of a customer complaint with regard to malfunctions in the functions described above, check the function with activation via the diagnosis (component activation) and, if necessary, inform the customer of the facts.

Diagnosis instruction

CAUTION! Activation via the diagnosis

With the engine off and ignition switched on, activation via the diagnosis for the functions concerned continues to work, except in the case of the seat heating (seat module) in E81, E82, E87, E90, E91, E92 and E93: the component activation only works if the engine is running or the seat heating was switched off beforehand (LED OFF on the centre console switch cluster).