[nissubaru]

I've posted a few times about this now but each time I'm at a different point in the diagnosis phase. It's also not the quickest thing to diagnose cause it doesn't just happen overnight.

Basically my battery died a couple months back and I got the car jumped. Drove a bunch but the battery still wouldn't charge. Got a multimeter and read 12.8V at the alternator. Ordered an alternator, albeit a shitty ACDelco one. Car hated it. Replaced it with a refurb'd Bosch AL0850X from FCP Euro. Everything was good for a couple weeks, took the car to the dealer for airbag warrant + inspection. Got the car back and a few days later the car wouldn't start which is when I began chasing all of this down.

Long story short, monitored the battery voltage with a multimeter after driving/before driving etc and the battery almost never sees 12.6V, reads anywhere between 12.1-12.4V. There is no parasitic draw that I can find and even after having the car sit at the airport for 5 days while I'm away for work the car started up just fine.

The battery did die a second time after getting it back from the dealership which is what prompted me to replace the alternator again as well as the battery with an exact replacement, registered through Tool32.

Now, I only did this the other day but my battery is still not reading 12.6V with a multimeter after driving. Alternator voltage reads ~13.5V which is almost identical to the previous alternator I got from FCP Euro. Currently the battery is at 12.3V after only 2 days of driving the car.

What the hell could it be? I swear the DME is just not telling the car to alternator to charge enough. At this point I'm almost out of ideas.

[frenchi]

Check and clean ground cable points on the chassis..common failure

[ctuna]

Did you replace with the identical battery?
Do you know what type and capacity battery the
car is programmed for. AGM or Lead Acid ?
amp hour rating identical or close?
Did you replace it with the same kind a capacity.
For Lead acid I would expect a alternator voltage more
in the 14 to 15 volt range.
I gather its lower for AGM.

[nissubaru]

Originally Posted by ctuna

Did you replace with the identical battery?
Do you know what type and capacity battery the
car is programmed for. AGM or Lead Acid ?
amp hour rating identical or close?
Did you replace it with the same kind a capacity.
For Lead acid I would expect a alternator voltage more
in the 14 to 15 volt range.
I gather its lower for AGM.

Battery was already replaced by the previous owner about 2 years ago. I really didn't want to replace it but was one of the only things I hadn't tried. I did check coding on the battery during all this troubleshooting and verified it is correctly coded at 80ah, non AGM.

KLASSE_BATTERIE
80ah

--
When I replaced it the other day I called around and found an identical replacement from an auto parts store in my town. Interstate MTP-94R/H7

[TemjinX2]

i would try re-registering the battery at this point. If its the DME like you said, that going to be a software issue. seems like you already tried all the big things.

[ctuna]

I have a lead acid interstate mtp 49/h9 I haven't really been having
trouble with it but I do put it on a battery tender once a month overnight.
Also my alternator voltage is more like 14.5 .

[jt335i]

It could be that there is a problem with the IBS (Intelligent Battery Sensor), or it might be failing, sending wrong info to the DME. This could result in your car not starting misleading you to think that the battery is dead. Try unplugging the blue IBS connector plug (basically bypassing it) and see if the issue happens again. If it doesn't happen, then the IBS needs to be replaced.

I could be wrong, but worth giving a try.
Good luck.

[nissubaru]

Originally Posted by jt335i

It could be that there is a problem with the IBS (Intelligent Battery Sensor), or it might be failing, sending wrong info to the DME. This could result in your car not starting misleading you to think that the battery is dead. Try unplugging the blue IBS connector plug (basically bypassing it) and see if the issue happens again. If it doesn't happen, then the IBS needs to be replaced.

I could be wrong, but worth giving a try.
Good luck.

Attachment 1699488

Couldn't find where I read this again, but it was on newtis.info. According to one of the BMW electrical manuals for the E90 it says not to replace the IBS unless codes related to the IBS are being thrown. Since I'm not receiving any codes related to the IBS + the next point I mention, I'm gonna leave it alone. But thanks for the suggestion.

It seems I may be a moron. I had been using my multimeter to test the alternator using the positive lead from the alternator + grounding the black lead/negative of my multimeter to the strut bolts. This was giving me the low voltage reading of 13-13.5V that I had been reporting all this time.

Well, when I moved my ground lead to the alternator housing or the oil filter housing itself since it's part of the engine, I was getting a solid 14.3V.

Idk exactly what this means but my suspicion at this point is a bad ground. Does anyone know all of the ground points? I can only find one, part #12427549393 which seems to be on the drivers side but I haven't personally gone looking for it yet. Do I need to jack the car?

[PhaseP]

That points to weak engine ground.

That part number you have is the engine ground, it goes from engine mount bracket to the side rail on the chassis, on driver's side.
There is a smaller ground strap which is for the ignition, it is called "interference suppression band" in BMW parts lingo, but its duty is not main ground, it is only ground for ignition coils. It is on the engine top passenger side, goes from the wire harness on top of the exhaust manifold to somewhere around there.

http://www.realoem.com/bmw/enUS/show...76#12427578869

[PhaseP]

Originally Posted by nissubaru

. Do I need to jack the car?

Yes.

From top you can see the engine mount connecting part of it, but with a 335 it must be more crowded there. My N52 I can barely see the ground strap from top of the engine.

[nissubaru]

Originally Posted by PhaseP

Yes.

From top you can see the engine mount connecting part of it, but with a 335 it must be more crowded there. My N52 I can barely see the ground strap from top of the engine.

I think I found the missing ground but its not the one we're talking about. Didn't know there was another, but it's on the passenger side by the wiper fluid tank. It looks like it has been cut though



Found this thread which led me to finding the cut ground wire.

http://www.e90post.com/forums/showthread.php?t=963362&highlight=ground+point

I'm still going to check under the car for the other ground wire but this is good news in my opinion. Definitely have an idea of what's going on now.

[PhaseP]

That is where one end of the "interference suppression band" that I mentioned in the earlier post is supposed to be. The "interference suppression band" is a braided wire AFAIK, so don't know why yours have a black sleeve left over there. The other end goes to a bolt on the engine valve cover that also ties down engine ignition wiring harness, from what I remember.

But, all that said, that "interference suppression band" is a relatively small wire, it is not for carrying the high current from alternator to the rest of the car. The engine ground strap that goes from driver engine mount top to the inner side rail of the car is the real ground. It is a thick heavy braided strap meant to carry all the current from the alternator to the rest of the car.

If you are measuring different voltage when referencing engine metal parts vs the car chassis metal parts, then the main engine strap that is at the bottom is your suspect. It means it is either broken so ground path is by different means now, through transmission drive train what not. Or it is not broken but corroded badly that is still not giving good low resistance connection.

You should definitely get the missing "interference suppression band" ground strap and place it, but also check the main ground strap as well. The main one being on the lower side of engine is suspect for corrosion being wet with road grime, water, salt etc. I had replaced mine more than 2 years ago, it was about to be broken completely.

[PhaseP]

Originally Posted by nissubaru

http://www.e90post.com/forums/showth...t=ground+point

I'm still going to check under the car for the other ground wire but this is good news in my opinion. Definitely have an idea of what's going on now.

Well, that "interference-suppression band" wire is for N52 from what I could find in realoem.com. Your is a 2009 335i. So I don't know, I can't find single part like that for your car. You may look also.
Maybe someone with a similar year 335 can chime in what theirs look like there. It may not be a separate part for your model and year, it maybe part of the wiring harness, I don't know. There is a remainder of a cut wire/cable there in your picture though.

[PhaseP]

That cut off connection may even be an aftermarket addition removed later on. You need input from other 335 (N54/N55) owners to tell whether you are supposed to have that additional "interference-suppression" ground strap or not with your engine.

In any case, as I said that one even if it was missing is not for carrying the main alternator current.

[nissubaru]

Originally Posted by PhaseP

That is where one end of the "interference suppression band" that I mentioned in the earlier post is supposed to be. The "interference suppression band" is a braided wire AFAIK, so don't know why yours have a black sleeve left over there. The other end goes to a bolt on the engine valve cover that also ties down engine ignition wiring harness, from what I remember.

But, all that said, that "interference suppression band" is a relatively small wire, it is not for carrying the high current from alternator to the rest of the car. The engine ground strap that goes from driver engine mount top to the inner side rail of the car is the real ground. It is a thick heavy braided strap meant to carry all the current from the alternator to the rest of the car.

If you are measuring different voltage when referencing engine metal parts vs the car chassis metal parts, then the main engine strap that is at the bottom is your suspect. It means it is either broken so ground path is by different means now, through transmission drive train what not. Or it is not broken but corroded badly that is still not giving good low resistance connection.

You should definitely get the missing "interference suppression band" ground strap and place it, but also check the main ground strap as well. The main one being on the lower side of engine is suspect for corrosion being wet with road grime, water, salt etc. I had replaced mine more than 2 years ago, it was about to be broken completely.

Missed your reply earlier about the interference suppression band. Like you, I also found that it is something on N52's on RealOEM but couldn't find anything on the N54.

After I made my previous post I went out and jacked up the car and took a look at the main chassis ground. It didn't look too bad but it's a rubber shielded wire so I gave it a squeeze/bent the wire a bit and it was super crunchy. I read that this might loosen the corrosion on the wires and improve the ground but I didn't really notice any improvement at the time.

I ran down to AutoZone and grabbed a 4 gauge switch to starter wire to test whether or not replacing the interference suppression wire would make a difference and to my relief it definitely did. I was finally seeing 14.1-14.2V at the bolt I was using previously, but only ~13.8V at the battery which I found a bit suspect. However, I'm glad you chimed in here because you pretty much confirmed my suspicion about the interference suppression band not being the exact problem because it is not the main chassis ground. I'll probably end up removing the wire I added today since I'm not convinced it should even be there, despite the cut wire left behind? It's just a temporary fix to prove the solution. I'm gonna go ahead and get the replacement main ground wire ordered asap.

Thanks for your input. Will update thread with final solution

[starrdon]

please help!!!!!!!!!!!!!!!!!!