Hit 70k miles. Car is fighting back (help)

Hi everyone,

I've had a relatively smooth sailing ride with my M3. I've owned it since 38k miles, and aside from regular maintenance I've done preventative work like the idle control valve, throttle actuators, and fuel breather valve (among other things)

I recently hit 70k miles and have been having some issues. My car started to stall when coming to a stop, without any codes thrown. I assumed this was the fuel breather valve which I replaced - doing the spark plugs at the same time.

I've now since had the same issue, although the car has now been going into limp mode and stalling out when coming to a stop. The only code I've been able to scan was P1209. I've been able to come across a few other codes/possible issues. Would love to get your thoughts on what it could potentially be. I'm attaching a summary of scanned codes from a shop I took it to today. I was on the way to get my oil changed and hoping the shop could figure out the issue and I did have some random rattling under acceleration which I've never heard until today. I'm picking the car up later this evening hoping that has subsided.


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Update 10/1
Car completely stalled and gave out, and will not start back up.

Errors received:
Driving stability! Drive moderately
DBC malfunction! Drive carefully
Start-off assistance inactive
Increased battery discharge

And right before the car shut itself off while driving, I got a transmission malfunction warning and the DCT shifter started clicking when it came to a stop. No outside transmission noises.

Car is broken down at the moment and I'll need to get it towed.

Rattling: check the donut gaskets between the x pipe and headers and heat shielding around there. While you're at it have a look at all the ground cables under the car and up top.

spammysammich wrote

Rattling: check the donut gaskets between the x pipe and headers and heat shielding around there. While you're at it have a look at all the ground cables under the car and up top.

Will check on that. Also should mention my car is catless, which explains the catalytic codes.

Still on the original battery and alternator? Get them tested

the brake booster went out on my car prematurely and caused a limp mode. i'd explore that if you're getting a code for it.

Could be a few things. First check battery voltage. It could be the original battery. I replaced mine that was holding at 12. Car started no problem but would randomly throw a SES/Increased emissions every couple hundred miles, im catless and tuned. Regarding brake booster plausibility with these cars 99% of the time it's the vacuum pressure sensor. You can save a ton of money by just replacing that sensor with a map sensor instead of the entire hose/vacuum pressure sensor It's $17 on Amazon. Pop your hood and look to see if you can see any brake fluid spilled on on the sensor ( it's right below the reservoir) I just had all these codes about a month or 2 ago and that was my issue

nycplumber wrote

Could be a few things. First check battery voltage. It could be the original battery. I replaced mine that was holding at 12. Car started no problem but would randomly throw a SES/Increased emissions every couple hundred miles, im catless and tuned. Regarding brake booster plausibility with these cars 99% of the time it's the vacuum pressure sensor. You can save a ton of money by just replacing that sensor with a map sensor instead of the entire hose/vacuum pressure sensor It's $17 on Amazon. Pop your hood and look to see if you can see any brake fluid spilled on on the sensor ( it's right below the reservoir) I just had all these codes about a month or 2 ago and that was my issue

Any chance you'd have a link to that exact part on Amazon?

https://smile.amazon.com/gp/product/B07HJ5ZPVR/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

I originally bought the BMW replacement including the hose and quickly ruled that out, replacing just the sensor is the way to go. There's a thread with some pictures that I believe I commented on, will post it here too if I find it.

I didn't have any codes but the vacuum pump seemed to be running more than it should, all set now and on to the next fix.

https://www.m3post.com/forums/showthread.php?t=1338052

2011e91 wrote

I didn't have any codes but the vacuum pump seemed to be running more than it should, all set now and on to the next fix.

https://www.m3post.com/forums/showthread.php?t=1338052

Thank you! Just ordered. Will report back

So far so good. I believe the vacuum pump was the issue. I also replaced the fuel breather valve 2 weeks prior.

Updated the original post.

Update 10/1
Car completely stalled and gave out, and will not start back up.

Errors received:
Driving stability! Drive moderately
DBC malfunction! Drive carefully
Start-off assistance inactive
Increased battery discharge
(Car is catless so the photo below shows increased emissions)

And right before the car shut itself off while driving, I got a transmission malfunction warning and the DCT shifter started clicking when it came to a stop. No outside transmission noises.

Car is broken down at the moment and I'll need to get it towed.

I know I need to get the codes scanned but has anyone ever had this issue? I had to manually force the car into neutral since the car wouldn't start back up in order to get it off the road. It died under load so I can't imagine it's entirely battery related as the car was driving at the time..

Battery was replaced 11/19

If the battery wasn't coded and registers correctly it could be shot. If it was, your alternator/voltage regulator could be shot. Sorry if I missed it but were all the recalls done on his car ?

spammysammich wrote

If the battery wasn't coded and registers correctly it could be shot. If it was, your alternator/voltage regulator could be shot. Sorry if I missed it but were all the recalls done on his car ?

It was replaced with an OEM battery almost 3 years ago now and ran without issue until recently so I believe it was coded correctly. Had that done at the dealer.

Alternator could be an issue I suppose. I believe all recall work has been addressed unless there was a recall recently I am unaware of.

There were a total of 3 recalls. Two of which could shut a car down suddenly or start a fire. Better make sure.

Also depending on storage conditions and usage patterns you could definitely run down one of these batteries in 3 years, not unprecedented. These cars HATE low voltage and multiple systems go crazy when they dip below 12.

spammysammich wrote

Also depending on storage conditions and usage patterns you could definitely run down one of these batteries in 3 years, not unprecedented. These cars HATE low voltage and multiple systems go crazy when they dip below 12.

Just checked using my VIN, no open recalls.

I drive about 500 miles a month. Do you think purely a battery issue would shut the car down mid drive? I didn't think solely the battery could do that while the car is powered on but I suppose if it's giving all of these other errors that could effect it.

A dodgy alternator could kill a car mid drive or bad grounds. It is easy to get an alternator tested. And a bad alternator/voltage regulator will kill the battery. Make sure your IBS system is plugged in.

My car threw all all kind of codes when then battery dropped to 12.4V. It didn't shut down the car or put it in limp mode tho. The codes went away after replaced the battery! So I would definitely check the battery and alternator to make sure it within specs. These cars seem extremely sensitive to low battery voltage.

Managed to get it running today. A jump start - struggled a bit but it turned on. Was able to at least get it to my shop.

Only error code thrown during this 10 minute drive was the increased battery discharge warning. So most likely battery or alternator I assume..

Alternator and battery shot.

The failure all at once was spectacular. At least the car is up and running at full strength again. Appreciate all the input.

Is the battery properly coded/registered to the car with IBS connected?