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Discussion Starter #1
Hello to you all here first of all and glad to have become part of this community.

Usually I'm not the forum type of a guy but maybe here I can find help where nobody else can provide me.

I bought a used 525d, 2012, 160kW manual transmission last year ago. Everything was fine with the car, used it daily and really was happy with it.

Until last June/July.

One morning I came to my car at the parking lot, unlocked it, pushed the start button and the car starts cranking... and it cranks, and it cranks for 10 seconds or so and I get an Drivetrain error. I push start/stop again, again starts the crank cycle but no luck again... Steering wheel error this time. I tried it a few times and after that the car started and drove perfectly for the next month or so.

Then the problems kicked in during July again, but this time much more frequently. I went to the local service centar, they made a whole system check and noticed a TON of random fault codes in the system. After clearing the codes they've also swapped in a new battery, changed the crank and camshaft sensors but still no luck. Random start problems were a thing for the next month. I was at the BMW service centar as well, and even they couldn't find a problem.
I was nerved by all of that until all the problems have vanished by themselves.
I drove the car fully normally for the whole summer, fall, winter and was pretty happy that the poltergeist was gone.

But now it's back, with a vengeance.

Problems have hit me again two days ago. Again the car cranks but no start. Again getting Drivetrain, steering wheel and ignition on messages. On top of that the rev counter dances around the place when I turn the car on (just power, no cranking).

Could it be that it's got to do something with electrical bits. I know that electronics act up as hell when grounding isn't good but I have no idea where to start troubleshooting since nobody in the service shops wants to deal with it.

I've shot even a video of this hell im going through
https://photos.app.goo.gl/ZdLbQvZNrXMfi8ym6

hopefully someone can give me some insight what to do next.

Cheers

Karlo
 

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375 Posts
My first thought was "new battery" but it seems you already replaced yours. I'm thinking you have a bad ground unfortunately.
 

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Discussion Starter #3
Yes, the problems were present even with the new battery.

A small update for todays testing:
I've enabled the hidden dashboard menu and went to check the system voltage and it was reading between 11.7 and 12V. In this state there is no bloody way I was able to start the car. It kept cranking but the errors popped up again (but this time the rpm gauge didn't do the possesed dance).

By some wierd choice or star and moon positioning in the sky, the car started after a few dozen tries.

System Voltage when the car is running is around 13.6 - 14V. Highest value is right after start, then it gradually drops to around 13.6V.

I've let the car run for a while then turned it off. The system voltage reading was around 12.6-12,8V and the car started without any problems.

Could it be that the battery is already dead? Or is it just some grounding/connection problem?
If it is the later, where the hell should I begin to troubleshoot :(
 

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Munich Mark - 2014 535XD
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When they changed the Battery was it coded at the time, BMW requires this...

For now use a Charger when parked overnight, thinking may be some short to ground leaking voltage somewhere... Tough one these Electrical Gremlins...
 

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Discussion Starter #5
@MunichMark: yes, the new battery has been coded in, or so they say at the workshop. Is there a way to check this statement from my side?

Further progress today: as you have proposed, I've left a charger overnight to pump up the battery. It topped up the battery with a 4-5 Ah of juice and that's about it. The problems still are present. Also, took a V-meter to the battery before charging it, it was reading 12,1V what seemses a bit low (true, all leads were connected to it)
However, I went a bit balkan retard today since I was getting a steering wheel error all the time mixed with a few drivetrain errors. I took a few whacks at the steering column with my hand during cranking and the car started without any problems. Don't know if it was a coincedence or not but will keep a closer eye on this sceintific approach during failing next start.

On another note, I was monitoring the system voltage during my drive back home (some 100km). The voltage never dropped below 13V and while brake regeneration is active or when I remove the foot from the throttle it goes up to 14.5V. I'd say everything is normal here...
As I said before, during the drive everything is perfectly normal, like I'm not having any issues at all.
 

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Munich Mark - 2014 535XD
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