Awest91

Ok so I have an 08 535i with sport package and iDrive and i have a very frustrating problem going on.
(Please don't reply if you're going to say something negative, I have had enough headache dealing with this. Thanks)

Ok first off (This may or may not be the cause of the problem but most likely is) About a month ago I installed a very high powered aftermarket subwoofer and amplifier by tapping into the under seat subwoofer wires that run back into the trunk for the low level bass signal, the positive and negative terminal on the battery for power, and the cigarette lighter fuse in the trunk for the remote turn on.

Everything worked perfectly fine (I know a lot about car audio I've been doing it professionally for many years so I know it wasn't an installation related mistake) and after about 30 minutes of driving listening to music the car threw a few warning messages on the iDrive.

1. transmission malfunction: functionality or display of gear selector position may malfunction. It may be possible to engage a gear without depressing brake pedal

2. DBC malfunction:
Dynamic brake control (DBC) is not active during emergency braking. Drive with caution

3. Drive control system!:
Driving stability
Drive control system malfunction. Reduced driving stability in curves. Drive moderately

So I pulled over to turn the car off and back on to see if it would go away but when I tried to start the car again it wouldn't start and continued showing the same messages along with the "P,N,D,M/S" lights on the gear lever fading/dimming. (Btw I have the electronic gear shifter, not a normal one where you manually move backwards and forward to put it in park/neutral/gear) I tried having a someone jump start it, I checked every single fuse, looked by the battery and under the hood and saw nothing out of the ordinary. I got the car towed home and the next day I decided to remove the amp and sub to see if that fixed it and it didn't at first but about 2 days later I randomly went outside and tried to start it and it started right up with no warnings or any problems at all.

So I'm driving the past few weeks and I decide to put in a smaller amplifier and door speakers (how stupid of me, I know, but I figured the power draw from my 13.5" JL audio subwoofer and 1000w amp was too much and this normal size set up would be fine). Install went fine again, I drove around for a few days and parked the car at home one day, went out later to start it and same thing. All the same warning messages so I removed the smaller amp and door speakers and returned everything back to how it was but this time it's been close to a week and it still won't start.

I tried unplugging the battery, checked all fuses, checked everything like last time, and then again to make sure I didn't miss anything and still nothing. I bought an agm safe battery charger and charged the battery hoping it would fix it, still nothing. A few days have gone by since and I got in the car yesterday and saw a few new messages along with the same ones that have been on this whole time

The two new ones are:

Start-off assistance:
Start-off assistance inactive caution, vehicle may roll back

Battery charge level low:
Battery heavily discharged. Charge by driving for a longer period or using external charger


And also, I just bought the Bavarian technic obd2 tool about 2 months ago and I've looked on there at a few things but this is the first time I've ever used it so everything is still kinda new/confusing but If you guys have any suggestions/ideas I can extract info or real time values off of there to see if that's the reason/cause

Thanks in advance

pcy

If I were you, I'd remove the battery from the car, fully charge it, then LOAD TEST the battery.

Better yet, if you can, get a new battery, install it, clear all the codes, and go from there.

seanjordan20

If you put an audio system in without backup power then it is your power. Your alternator is getting over worked. Your battery cant keep a sufficient charge to keep the car going. Uninstall everything, you might need a new alternator if that one is old (might be on its last leg), Buy a new battery (if that is old), charge it up and you should be fine.

The power is too much for the old system. If you plan to do the setup again buy the biggest battery for your car and maybe a bigger alternator. I would have put a backup in so it can draw power from there because these car a very sensitive and the slightest power draw it will go crazy. If the setup is right you should have no problem. I had two 12" subs with a 2500 watt amp for about a year and had no problem so I am sure it is set up wrong for the type of car you have.

Awest91

I actually forgot to write that I have an e90 3 series tjat I pulled the battery out of which is fairly new and I Swapped the e60 battery for that one but it still won't start or change anything. I haven't tried that since the new codes came up so I'll try that again

Awest91

I didn't think it would be a problem because I have had the system in my 2006 e90 ever since I got it and my 5 series is newer so I figured it would be fine but I was wrong obviously. Thanks I'll def try a new alternator but it's gonna suck if it's not that

seanjordan20

Before you try a new alternator try a fully charged battery with no stereo. See if everything works fine. You can have you aternator checked too before swapping it out

evolotion

if it helps when my alternator died it DIDNT put on the battery warning light on the dash, all that happened was one by one things started lighting up, SRS, ABS EML etc untill the car just flat cut out. I also have a decent ish sound system ~1200W RMS am not shy with it, and no battery issues.

In future perhaps wire the +12v battery connection to the car side of the sensor on the positive lead on the battery so the car knows current that is going to the battery is actually going to the battery and not your amplifier. IIRC (tho id have to check) I took the +12v feed for my amplifiers from the constantly live screw post in the boot fusebox.

pcy

Check all the fuses. With all those swaps, one of the fuse/relay may have blown.

Awest91

The first thing I did was take the stereo out and charged the battery fully but still nothing and I thjnk from trying to start/diagnose the proble is what caused it to drain and show the new codes or maybe I left something on. And I know the alternator can be tested and I have just about every tool you could imagine even electrical testing equipment cuz I do car audio for a living so I would do it myself if I get the correct info on how to do so

Pistratoaie

What about registering the battery when you changed it? when we changed our X5 battery all sorts of warnings went off, until we drove it to the shop to get it registered and that solved everything. otherwise it does sound like the alternator could no longer be sufficiently charging the battery and once the battery has been discharged it will do mysterious things.