In the event of problems with increased closed-circuit current, it is frequently the case that this must be determined during Service. With the conventional procedure, a shunt resistor must be fitted at the earth strap of the vehicle.
All vehicles with an intelligent battery sensor on the earth pole (as of E60) automatically run a closed-circuit current measurement approx. 90 minutes after idle status (see Procedure). The results are totalled in the engine management system in a closed-circuit current histogram. The closed-circuit current is assigned a current range minute by minute (0-80 mA, 80-200 mA, 200-1000 mA, >1000 mA) (only if all auxiliary consumer units are switched off, see Procedure). Each current range contains the information as to how many minutes the closed-circuit current was in a particular range.
The minutes counter is restricted to 15360 minutes (around 11 days). When this value is reached, counting takes place only the ranges under 15360 minutes. The values can only be read out and deleted using a service function.
As a rule, the closed-circuit current may only lie in the range 0-80 mA. A closed-circuit current in the other ranges may only occur briefly and sporadically. 11 days after resetting the closed-circuit current histogram, it is usually the case that the current range 0-80 mA will have accumulated a time of 15360 minutes (approx. 11 days). From this moment onwards, the closed-circuit current histogram is meaningless, as the duration of measurement can no longer be reconstructed.
If the closed-circuit current histogram is reset using the service function, a closed-circuit current measurement can be carried out using the data of the intelligent battery sensor. After the measurement, the closed-circuit current histogram can be read out using the service function.
The closed-circuit current measurement begins approx. 90 minutes after the idle state is reached. The idle state is reached when the following conditions are met:
If any of the above conditions is not kept, the current ranges are not counted upwards in the closed-circuit current histogram. Under certain circumstances, a defective control unit can also be responsible for this condition. In this case, the test module for energy diagnosis should be run.
It is recommended to run a closed-circuit current measurement over more hours. The closed-circuit current measurement is interrupted immediately if the vehicle is woken up and only continued if the idle status is present for another 90 minutes.