BMW Questions? Ask a BMW Repair Expert for Answers.
Hi im kevin so can you confirm if you run car today that everything is normal?
The only real explanation is that the alternator was not charging the battery .now its likely that the alternator is the underlying cause but until this reoccurrs its difficult to say 100% .
This code refers to a comms issue between the engine e u and alternator does code clear down ?
The easiest way to explain is that your car is fitted with a smart charge type system .so the voltage can change as the battery needs more or less with the intention to inprove fuel econemy and efficiency .this means that the alternator is switched on by input signal rather than the old type of straight voltage .the car is basically saying ive asked for an increase in charge voltage but no change so a no comms code is logged as the car believes the alternator hasnt recieved this message
In most cases the only way to 100 % confirm would be to use an oscilloscope to check signal input from the engine control module but you would need the fault to be present at the time .
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That is possible thats why you would need to scope when fault occurrs to confirm signal
I dont have a wiring diagram on your model so i cannot confirm this test .your first port of call would be to ensure the connections on alternator are clean and tight
Il opt out of the question another tech may have scematic and will be able to assist further