As for E6X/E8X/E9X “intelligent” alternators which are managed via BSD (Bit Serial Data) interface are used, the simple verdict “charges/don’t charge” is not enough!


1. Check, if the error message memory contains any error messages regarding IBS, BSD interface or alternator itself. If there are some, causes of these problems have to be eliminated on the first hand! While there are problems with IBS or BSD interface, the alternator will not charge the battery on full mode! For this reason:

a) connect INPA;

b) open ../F4/F1/F3 and F4/F3/F1 (if the Error message list is recently deleted).


2. If there are no error messages regarding IBS and BSD interface:

a) connect a multimeter to the battery (range: 20 VDC);

b) start the engine;

c) disable the large consumers: heating of steering wheel, seats, and windshields;

d) connect INPA, open test menu of alternator ../F6/F2/F1.


When changing the voltage, inquired by a alternator, make sure that the voltage on battery clips changes according to the required value of alternator.

Note: voltage on battery clips typically will be for around 0.5 V lower as required for a alternator. These 0.5 V is a voltage drop in wires “alternator – battery”.


Attention! After completing the test, don’t forget to restore DME control of alternator’s voltage!


If alternator “doesn’t listen” to commands – due to some reason its management don’t work as it supposed to. Check BSD connection, alternator’s management module has to be replaced with OEM (if after repair it was replaced with “universal” one).


3. If alternator “responds” to commands of DME, check the ability of the alternator to develop necessary current.

a) open alternator data menu, using INPA: ../F5/F5/Shift+F2;

b) turn on all significant consumers: low and high beam front lights; heating of steering wheel, seats and windshields;

c) evaluate max current, which the alternator is able to maintain in idle:

Max current in idle has to be around one half of rated current of the alternator, it means:

  • around 50 .. 60 A, if rated current of a alternator is 120 .. 130 A;
  • around 80 .. 90 A, if rated current of a alternator is 160 .. 180 A.

Increasing RPM of the engine (to 1500 .. 2000), max current of a alternator has to increase and reach over 100 A.

If max current which is developed by a alternator is reduced, perform the repair of the alternator. Possible defects: damaged (one of 3 phases) diodes, bad connections (oxidized), worn blades on a worn collector.


If you want, you can use also test block of alternator ../F9/Shift+F1

Here you will find test-bits of the alternator, and also you can activate a alternator’s self-test. During the test, DME will sequently change the voltage, required by a alternator (15.0/14.5/14.0/13.0 V) and will analyze its performance. True thou, this test doesn’t check the ability of max current.

P.S. If you have found this entry, obviously – the car has some problems with battery (energy). Please, check IBS data, SOC and SOH of the battery!