Car Shutting Off While Driving & Stall at Idle

[F10_M5_Competition]

2015 m5 with 50,800 miles. Exhaust, catless downpipes, Turner Motorsports tune.
OBD Reader Codes: P0030, U0100, U013C

A block away from my house, I stop at a red light and the engine just shuts off on its own (not start & stop, I never use it.) Throws a bunch of random errors. Electronics etc still working. I turn the car back on, it idles for 10-15 seconds and engine shuts off again. I turn it on one more time, and this time I put it in drive to see if I can move it out of the street. It runs for the same 15 seconds or so and shuts off, luckily I managed to roll in neutral and park it lol.

My initial thought is, either battery must be really low on juice, or possibly a loose connection to the DME's or something. I open the trunk, remove the battery and connect it to a trickle charger. The trickle charger shows the battery was at 33%, so I charge it to 100% over 8 hours or so.

Plug the battery back up, try to turn the car on, but when I go to put my foot on the brake it feels stiff. Ignition/Auxiliary mode and all the electronics turn on, but brake pedal still feels stiff and engine isn't turning on at all. After a few minutes of googling shit and checking the DME and O2 sensors, I noticed one of the four bolts from the DME brace tower was missing. Regardless I get back into the driver's seat and try to start the car up, which it finally did. Maybe because the battery needed some time after being reinstalled, idk. But anyhow, it still ended up cutting off after 15 sec of idle or so.

Spent the next 30 minutes googling shit again in disappointment, and decided to put some weight on top of the DME brace tower to see if stabilizing it would maybe let it run without shutting off. Well, I try to turn the car on and fuck me, the car actually started up and was able to idle without the motor cutting off. Now, I have no clue why it was able to keep running this time around. Was it that the battery just needed some time? Or did putting weight on the DME brace tower help?

Anyhow, I went for a casual drive to help the battery charge everything up and stretch the car's legs. Pulled into a gas station, and it cut off the engine again. No biggie, turn it back on and continue on my way to get on the freeway. 15 minutes cruising problem-free on the freeway, when all of a sudden the motor shuts off on an exit goin like 50mph. I slow down to about 25mph and press the start button, engine turns back on and I shift back into gear and keep driving. For whatever reason I try to put the car into M1 mode (my setting for full Sport+ everything) and engine cuts off again.

Long story short, I made it back home with the car shutting off more and more frequently the whole way back. So, need new battery? Fucked up ECU connections? Alternator? O2 or MAF sensors? I'm lost HALP


https://streamable.com/ryzg37

[fstm5]

From the codes that you have provided and from just a random guess it seems that your car is shutting off after a few seconds due to the ECU putting itself into a failsafe. Now i'm not saying this is what is 100% going on but if it had to be my guess there's most likely a sensor or something O2 related going bad and the ECU is freaking out and trying to prevent any further damage happening to the motor.

Also, U0100 usually translates to a bad connection between the ECU AND PCM, so again im leaning more towards a bad wire or connection or a loose connection possibly?


Orrrr your DME connections have a short or a cut somewhere lol


One positive side to this is that cold start sounds narly ass hell lol, whats your exact exhaust setup?

Best of luck

[F10_M5_Competition]

Originally Posted by fstm5

From the codes that you have provided and from just a random guess it seems that your car is shutting off after a few seconds due to the ECU putting itself into a failsafe. Now i'm not saying this is what is 100% going on but if it had to be my guess there's most likely a sensor or something O2 related going bad and the ECU is freaking out and trying to prevent any further damage happening to the motor.

Also, U0100 usually translates to a bad connection between the ECU AND PCM, so again im leaning more towards a bad wire or connection or a loose connection possibly?


Orrrr your DME connections have a short or a cut somewhere lol


One positive side to this is that cold start sounds narly ass hell lol, whats your exact exhaust setup?

Best of luck

Thank you I really appreciate your input man. Going to look over all of the connections again, I actually came across a thread describing something very similar and bolting down his DME brace did the trick: https://f10.m5post.com/forums/showthread.php?t=1578382

As for the exhaust it's a meisterschaft gthaus exhaust with evolution racewerks catless downpipes. Gnarly as hell is an understatement lol neighbors definitely hate me

[M5Rick]

If an O2 sensor is out the motor may behave like this, also worth checking both MAF's first.

[F10_M5_Competition]

Originally Posted by M5Rick

If an O2 sensor is out the motor may behave like this, also worth checking both MAF's first.

Roger. Anything specific I should look for? Like corrosion, wear or damage I presume?

[M5Rick]

Originally Posted by F10_M5_Competition

Roger. Anything specific I should look for? Like corrosion, wear or damage I presume?

Unless you take it in for BMW to check the O2's I think the only way is trial and error by replacing any O2's which look bad, of course clean MAF's with CRC spray and let them dry, if there's heavy oil mist on them it will cut out, can't really suggest anything else that fstm5 hasn't said already. GL.

[F10_M5_Competition]

Originally Posted by M5Rick

Unless you take it in for BMW to check the O2's I think the only way is trial and error by replacing any O2's which look bad, of course clean MAF's with CRC spray and let them dry, if there's heavy oil mist on them it will cut out, can't really suggest anything else that fstm5 hasn't said already. GL.

Much appreciated

[fstm5]

Originally Posted by M5Rick

If an O2 sensor is out the motor may behave like this, also worth checking both MAF's first.

That's interesting, when my pre cat 02 sensor went out all I got was an engine light nothing more, car was actually running smooth as well at least to the best of my knowledge.


It's crazy how complicated these motor's electronics can get

[fstm5]

Originally Posted by F10_M5_Competition

Thank you I really appreciate your input man. Going to look over all of the connections again, I actually came across a thread describing something very similar and bolting down his DME brace did the trick: https://f10.m5post.com/forums/showthread.php?t=1578382

As for the exhaust it's a meisterschaft gthaus exhaust with evolution racewerks catless downpipes. Gnarly as hell is an understatement lol neighbors definitely hate me

Yeah I'm definitely thinking it has to be a loose connection, I feel like the DME connection brackets are pretty brittle especially being around all that heat all the time, I can see how they would break and cause issues, shit even mine, one of the brackets is broken but luckily not to the point where it would come loose.

Wow I can't imagine how great that exhaust sounds, once you get it up and running definitely post up some clips

I live in cali so it's a bit of a risk of putting an exhaust especially with catless downpipes but I'm probably pulling the trigger soon

[F10_M5_Competition]

Originally Posted by fstm5

Yeah I'm definitely thinking it has to be a loose connection, I feel like the DME connection brackets are pretty brittle especially being around all that heat all the time, I can see how they would break and cause issues, shit even mine, one of the brackets is broken but luckily not to the point where it would come loose.

Wow I can't imagine how great that exhaust sounds, once you get it up and running definitely post up some clips

I live in cali so it's a bit of a risk of putting an exhaust especially with catless downpipes but I'm probably pulling the trigger soon

Thank you sir! Uploaded exhaust clip from a few months ago for your viewing pleasure. Just need to add in an X-pipe and it'll sound exactly how I want it. The turbo spool sound in person is INSANE.