Hey all,

I’ve been chasing an unsolvable issue likely electrical on my 2012 BMW M5 for a while now and would really appreciate any last insight before I would want to part out.

123000km (76k miles), car shuts off randomly, mostly when idling, coming to a stop, decelerating, mostly when warm. When it stalls, it gives a mountain of error codes (in the attachment, codes also vary) and random iDrive warnings sometimes: drivetrain malfunction (sometimes the red one), fake overheating warning, flat tire monitor, DSC, fuel supply, electrical power supply, replace battery warning etc. On the highway I sometimes feel a brief RPM dip with a check engine light, then it recovers without dying and engine light would disappear.

It can happen once every few hours or as frequently as every few minutes.

Starts back up right away most of the time, but occasionally would leave me stranded on the road for about a minute sometimes it wouldn't crank sometimes it would just keep cranking

Car is stock drives beautifully with no check engine light, no power loss, driving hard or more on the highway seems to delay the stalling but issue would come back later, driving gently in the city makes it worse, it would drive from one city to another and take on B roads like nothing.

Recently had an OEM flywheel replacement it was causing very similar issues, replaced crankshaft positioning sensor, new battery, tested alternator seems to be fine, tried swapping an EKP module from another M5. Any advice or direction would help me a lot and would greatly appreciate anyone share with me how you solved it if its happened to you before.

TIA

I want to help but electrics are not my forte', it's likely a short somewhere I'm guessing. All I can suggest is to check the ground wires and others everywhere especially around the DME's and their holding frames.

*KurtsM5, any ideas..

M5Rick wrote

I want to help but electrics are not my forte', it's likely a short somewhere I'm guessing. All I can suggest is to check the ground wires and others everywhere especially around the DME's and their holding frames.

*KurtsM5, any ideas..

Appreciated sir

Can’t open that pdf for some reason, but sounds like a bad battery, bad battery connections, or maybe even alternator issue to me.

Saw you’ve looked at these already, is the battery OE or better specs? AGM?

M5_Raz wrote

Can’t open that pdf for some reason, but sounds like a bad battery, bad battery connections, or maybe even alternator issue to me.

Saw you’ve looked at these already, is the battery OE or better specs? AGM?

Thanks will look into these, yes AGM and similar specs I believe

Hmm I had this issue on a different German car a long time ago and it was the camshaft or crankshaft position sensor (can’t remember which). Something to look into because both can cause random shut offs while driving.

M5_Raz wrote

Hmm I had this issue on a different German car a long time ago and it was the camshaft or crankshaft position sensor (can’t remember which). Something to look into because both can cause random shut offs while driving.

Crank sensor replaced already I think it helped slightly but issue didn’t fully go away

Update: Replaced HPFPs, HPFP gaskets and the new wiring adapters welded in, original pump on the driver side (bank 1) was confirmed leaking which very likely caused the stalling issue and intermittent rich running. However after replacement the passenger side is now giving a high fuel pressure 2 code too low and running lean, misfire on idle and stall when driving possibly a new pump is defective so next step is swapping the old one back for bank 2 in the shop and will update

M5Rick wrote

I want to help but electrics are not my forte', it's likely a short somewhere I'm guessing. All I can suggest is to check the ground wires and others everywhere especially around the DME's and their holding frames.

*KurtsM5, any ideas..

I would be checking every single ground point.It has there are two on the d m.E's, there's one under the bonnet front right side car, and of course, the ground on the battery itself. This is something dumb.If it was physically broke, it would be fucked up.All of the time. I am electronics engineer since I joined the navy in eighty two.So I have a little bit of a clue.Try that.I hope it works out for you.I don't want you to part the car out.

Update – FIXED

Turned out to be the driver side HPFP leaking which was causing the intermittent rich running and random stalling, the fuel has washed down the oil on that pump. Swapped back the defective new passenger side pump with its old one car is now running perfectly no more stalls and no more running rich so far.

M5 Hayden wrote

Update – FIXED

Turned out to be the driver side HPFP leaking which was causing the intermittent rich running and random stalling, the fuel has washed down the oil on that pump. Swapped back the defective new passenger side pump with its old one car is now running perfectly no more stalls and no more running rich so far.

Wow that was quite a rough trip Hayden, so the new HP pump was defective...

M5Rick wrote

Wow that was quite a rough trip Hayden, so the new HP pump was defective...

Yep the old pump on bank 1 was leaking, 2 new pumps were installed by mechanic but new one on bank 2 was not working properly so reused the other old pump that was good. I’ve also done some research about the newer HPFPs BMW use from what I’ve found they can leak internally, which is also exactly what my mechanic told me after test driving my car, they can cause intermittent or permanent rich conditions at warm idle or maybe low load or decel but the lack of other symptoms making it painfully hard to find out. So happy that I’ve learned something about these buggers and most importantly I can now finally sleep tight

Another update to this: after running for a month unfortunately the stalling issue came back so it was not caused by the HPFP, it only fixed the running rich issue. I would say that only fixed 80% of the problems

Here are some codes I found any help is appreciated, also has intermittent long cranks, sometimes won’t start even after manually shutting off

DME1

CD8F01
LIN, communication (intelligent battery sensor): missing
218404
Starting voltage converter / starter generator, control: line interruption
CD9437
FlexRay, message (request wheel torque drive train total stabilization / target distribution longitudinal torque front axle rear axle, 43.1.4) in the event of undervoltage: communication error

Junction box electronics

8020DB
Battery sensor, WakeUp line (WUP): Short circuit to ground or line break
802093
Compressor valve: Short circuit to positive or open circuit

Car Access System

930751
Driver KL15: Short circuit in battery voltage
D91410
DME CAN message data drive train: Missing or CRC error