Serious Safety Issue on BMW E90 2010 (Voltage Issue)

Question

My car has the below symptoms, and it caused the car to stall and lose all the electrical and engine power all of sudden for 3-4 seconds while driving at 50 mph on the motorway. Milage is around 95000miles. Its a BMW 2010 E90 Saloon with N43 engine.

Symptoms can be seen on the video link attached below;

https://www.youtube.com/watch?v=ZPbjUZ_8v7w&ab_channel=ozan

(1) When the car is parked (gear at P), and the key is inserted and brake applied in order to start the car, after pressing the start/stop button, the car only turns on the electricity, and it does not crank. The car has no symptom such as rough idle or long crank. Usually the crank is good and the car starts okay.

(2) However, after 30-40min driving, very often, the interior lights and front headlights starts to flicker. The lights flicker even more when slowing down or while idling at traffic lights. When this starts to happen, while parking the car in low speed, steering wheel feels anormal (feels heavier).

(3) When the above symptoms happening, if I park the car, and press the start/stop button to switch off the engine- it causes all the electrical components to stop functioning. Even the key in the key fob remains locked. Radio, dashboard, interior lights etc. does not work. It remains with no electrical power until a vibration (caused by opening and closing the doors) triggers everything to restart.

(4) Only once in August 2021, the whole engine cuts off power after driving 3-4 miles at a motor way at around 50mph. None of the components worked and the electricity restarted after few seconds. Since this happened, I did not drive the car very much as it does not feel safe anymore.

(5) Time to time, while driving, dashboard shows faults related to ABS/DSC related problems. When these faults appear on dashboard, usually they stay on the screen for as short as 2-3 seconds.

Additional Info:

(1) The car has a relatively new battery (purchased on January 2021), and the product name is as below; “Varta Start-Stop Silver Dynamic AGM 570 901 076 E39 12Volt 70Ah 760A/EN Starter”

(2) I drove the car while the battery voltage value is activated on the dashboard (via hidden menu). The voltage value fluctuates very quickly and spikes between values 12 and 14.5 simultaneously when the lights flicker.

(3) The battery, alternator, as well as the (+) and (-) cable connections on the battery of the car was tested recently at my local trusted mechanic, and I was informed that they look fine.

(4) The fault was thought to be caused by a poor connection between +battery cable and fuse box (this recall repair was done in 2017 by BMW), and after the inspection at BMW and I was informed that this connection is good.

Any idea what might be causing all these?

Thanks

SHOW LESS

yaser · Accepted Answer

Well, if you are sure that the battery and alternator are good and the connections are fine, then you need to find a good mechanic who is expert in BMW electronics to find out the issue. Unfortutanetly, those machines are very complicated and you need an expert.