The BMW E60 520d (N47) 2008 LCI is experiencing an unusual issue where it does not crank or start.

[NevoBMW320i]

Approximately one year ago, the automobile failed me. Upon pressing the start button, there was no response or action. We contacted the breakdown service, and upon their arrival, the technician requested me to showcase the issue - at this point, the automobile unexpectedly resumed functioning. After recharging the battery, I proceeded on. There were no indicators or signals of caution.

Yesterday, I had the same problem where there were no warning signs, just the typical start-up process followed by silence while pressing the start button. On this occasion, I patiently waited for just 30 minutes, and to my delight, the engine started and the radio began playing. Typically, when my battery is low, the audio becomes muted. She has been functioning properly since, and as a precautionary measure, I have connected the battery charger.

I connected the OBD scanner and it detected 2 problems. The A0B3 CAS is experiencing a failure in the Starter Motor Terminal 50 and the LM voltage.

I find this situation unsettling and I may draw certain inferences, since this is not a function that I want for my BMW, considering that I use it on a regular basis.

1) The possible cause might be the battery, however it was installed in January 2022, so it is not considered old.
2) Mechanically, there are no issues. The starting motor functions properly and the vehicle starts without any problems, as it has done during its whole lifespan, including today, save for these two separate occurrences.
3) Fuses must be undamaged due to point 2

Therefore, I am faced with the possibility that either the battery is the issue or there is some type of sporadic malfunction in the CAS system. I would appreciate suggestions about the next steps to take in order to isolate this problem.

Thank you in advance

[johnmayerrr]

Obtain the battery voltage reading when the vehicle fails to start.

[NevoBMW320i]

I was expecting to take a more aggressive approach rather than passively waiting for the next disappointment.It may have a latency of up to one year

[NAVITEL]

I have previously encountered this issue on this platform, but I am now unable to locate the specific thread.
I will review it again later after I have had more coffee.
Additionally, do the remaining functionalities such as lights, wipers, and other components operate properly?
A cable defect in the B+ circuit causes a complete shutdown of all electrical functions, including the ability to lock and start the device.

[NevoBMW320i]

Although I did not precisely test those features, the central locking, interior door lighting, and alarm systems all operated correctly.

[NevoBMW320i]

After thoroughly examining the topic, it seems that a potential problem might be the deteriorating condition of both my alternator and voltage regulator. Another module is the IBS module. Both scenarios would result in electrical complications that the automobile would not like - what are your thoughts?

[NAVITEL]

Consider attempting the procedure by disconnecting the blue line, which I believe is related to the ibs.
I have never been knowledgeable or interested in electrical systems.

[diablos_carcv5]

Due to its infrequent occurrence, diagnosing it will be challenging.
During my ownership of the e61 535d a few years ago, it functioned well. However, one morning, it completely failed to start. I disconnected the IBS and it suddenly became operational, then I reinstalled the IBS and did not have the problem again.

My suggestion would be to disconnect the power supply to the IBS and attempt to restart it when the issue occurs again.