[LegitRisk]

Hello again forum, I call on any of you for help, once again.

I’m a little stuck on this BMW.

2006 BMW 325xi with 3.0 and 6sp auto
Last 7: KV09002

So far, I’ll give a little run down of history so you can understand my circumstances as well as what I know of the current condition and how I received the car(skip to the TLDR if you don’t wanna read all this mumbo jumbo).

Bought the vehicle a month, maybe a month and a half ago for 800$, seller said it ran great, shifted great, needed window regulators and a brake booster but other than that car is “great”.


Picked up car, drove it home and on my drive home I noticed it was stuck in some sort of 3rd gear limp mode. Figured ah well screw it, shells of these cars go for a grand and a half or so where I’m from so ultimately it was a steal. Went to scan it and see what the deal was with the Christmas tree’d dash and the lack of shifts and had no OBD2 communications.

After researching, diagging, and consulting the forum I came up to the conclusion it had a bad JBE. After seeing online the price was a whopping 350$ for a brand new one I went off to the junkyard and acquired a JBE for 30$. Immediately half the dash lights turned off, OBDII communications were regained and the car shifted beautifully. I was incredibly impressed at how little I had to do in order to fix the whole major problem.

Next up came the clunking in the front end on braking, obviously this was remedied with a 200$ front end kit from Amazon, not terrible cost for parts and they seemed relatively quality, put in everything I could. Car still needs struts and other suspension parts but handles like a BMW should.

Lately I’ve been trying to tackle the lack of a brake pedal as the pedal doesn’t actuate till the floor but whilst doing so I’ve discovered that the car doesn’t like to stay running at an idle.


At an idle, the car will run but will appear to bog down, and almost stall at points. There was no present codes relating to this happening so I scanned it while driving and noticed one consistency. Whenever the vehicle was running rough the voltage was dropping down as low as high 11’s while running, keep in mind this was only under idle. When accelerating the system appears to charge as it should.

After researching this issue I noticed the symptoms mimicked a failing voltage regulator and figured, “well, the car has 200k. It likely could use an alternator” and threw an alternator at it without a second thought being in the past typically charging system issues have to do with the alt or battery.

Systems persist however only dropping as low as 12-12.5 now, which is the strange part. I read something about a failing IBS causing this and tried unplugging the IBS to no avail, caused the same condition.

Does anyone have any tips or advice on where to go forward with troubleshooting? If anyone would like a full code list I absolutely can provide. Please let me know, thank you.


TLDR; voltage is occasionally dropping to 11-12v at an idle and causing the car to run rough. This condition only persists when low voltage leading me to believe its voltage related. Car has new alternator. Battery is consistent for engine starts so likely not in bad condition. (I haven’t needed a jump yet!)


I would like to add I am in Florida so road salt isn’t a problem however the car has seen the north according to the carfax so I’m not putting it past it.


To add- I did use a voltmeter as well to check the voltage aside from my scantool and saw the same voltage drop at 3 points:
Engine block(-)/Alt(+)
B Neg(-)/B Pos(+)
Strut tower nut(-)/Alt(+)

[LegitRisk]

Something else to add as I saw something about it, there was a bog down/rough time accelerating so I threw a highly rated set of aftermarket coils and plugs at it. Supposedly ngk and oem equivalent but who knows. I did read that aftermarket coils could cause voltage spikes or have in other cases, however the bogging down/what appeared to be a misfire under load went away after doing so hence my hesitation to assume it’s a faulty coil pack situation.

[gbalthrop]

Originally Posted by LegitRisk

... 2006 BMW 325xi with 3.0 and 6sp auto
Last 7: KV09002... threw an alternator at it without a second thought being in the past typically charging system issues have to do with the alt or battery... voltage is occasionally dropping to 11-12v at an idle and causing the car to run rough. This condition only persists when low voltage leading me to believe its voltage related... I did use a voltmeter as well to check the voltage aside from my scantool and saw the same voltage drop at 3 points:
Engine block(-)/Alt(+)
B Neg(-)/B Pos(+)
Strut tower nut(-)/Alt(+)

If I understand correctly, you have rough running ONLY when alternator voltage drops, & alternator voltage fluctuates RANDOMLY, at idle?

Did SAME Voltage fluctuation occur with original alternator?
Is Replacement Alternator a "BSD Alternator" controlled with BSD signal from DME? (Violet wire in schematic).
Does Alternator Output Voltage stabilize at ~ 14.4V when BSD wire is disconnected from vehicle left rear of alternator?
What DME Fault Codes are present?
Is Large Red B+ wire between Starter & Alternator damaged/failing?

It would appear that one of the following applies:
1) Alternator is NOT a "BSD Alternator" (Make/Part#?);
2) BSD Connector is NOT making proper contact;
3) Damaged Violet BSD wire between DME & Alternator;
4) Other BSD Fault or faulty DME Output.
5) Intermittent B+ Supply to Alternator.

ISTA ScreenPrints of Alternator Wiring for KV09002 are attached to NEXT Post. Please provide answers to questions above, particularly any DME Fault Codes.
George

[gbalthrop]

Attached are two ISTA ScreenPrints related to Alternator wiring, Prior Post.
George

[LegitRisk]

Originally Posted by gbalthrop

If I understand correctly, you have rough running ONLY when alternator voltage drops, & alternator voltage fluctuates RANDOMLY, at idle?

Did SAME Voltage fluctuation occur with original alternator?
Is Replacement Alternator a "BSD Alternator" controlled with BSD signal from DME? (Violet wire in schematic).
Does Alternator Output Voltage stabilize at ~ 14.4V when BSD wire is disconnected from vehicle left rear of alternator?
What DME Fault Codes are present?
Is Large Red B+ wire between Starter & Alternator damaged/failing?

It would appear that one of the following applies:
1) Alternator is NOT a "BSD Alternator" (Make/Part#?);
2) BSD Connector is NOT making proper contact;
3) Damaged Violet BSD wire between DME & Alternator;
4) Other BSD Fault or faulty DME Output.
5) Intermittent B+ Supply to Alternator.

ISTA ScreenPrints of Alternator Wiring for KV09002 are attached to NEXT Post. Please provide answers to questions above, particularly any DME Fault Codes.
George

This is correct George, unfortunately it appears the rough running condition is only present when the voltage is fluctuating on the lower end. Car doesn’t feel like it’s hesitating/having issues until below 12.8 or so, maybe 12.5


The symptoms were very similar if not the same with the original alternator(which was factory, factory BMW logo and all its grime and glory). The voltage would drop however it would drop nearly a volt- a volt and a half lower than what it is currently, and the condition would be the same. When this happens, the dash goes from having the lights I’m about to share, to adding the brake light, and ABS light.

I am not sure as to whether the replacement alternator is a BSD controlled alternator, I just went off of vehicle fitment + whatever was highly rated on the site(Amazon). I can find part number and model shortly. (presumably it is as it has a voltage regulator with a single pinned plug same as my factory alternator.)

I will go pull a fresh scan on the car now and supply the PDF it gives me. I have not checked the wire between the starter and the alternator however I am not ruling it out as the person who sold me the car had said the starter was replaced so it’s very possible someone damaged something down there. The only thing holding me back is I have not bought a gasket set so if I remove the intake manifold it will be off for at least a few days while I get around to ordering a gasket set.

Bear with me while I get you a code list and thank you so much for your reply George. People like you make the world turn.


Edit: I will also test if the voltage fluctuates with the BSD wire unplugged.

[LegitRisk]

This is the pdf drafted by my autel for the codes. Anything that’s “absent” will go away and then return when the voltage drops(mostly can communication errors)

Testing the whole disconnecting the bsd line and running it now.


PDF


I believe the MAF sensor codes have to do with what appears to be a cheap aftermarket MAF I have yet to replace still.

Upon disconnecting the BSD wire and starting the car the voltage is hovering at or around 11-11.3 and has not gone down or up.

[LegitRisk]

Still stuck scratching my head on this. Unsure where to go.

[ptpending]

no magic here, if you bought unserviced car you'll invest money to keep it running to the price of the serviced cars
so, now you need new or low mileage alternator
you you should buy them until you get 13.8V while engine is running
same will be with automatic transmission, steering, suspension, air conditionion system....

[LegitRisk]

Originally Posted by ptpending

no magic here, if you bought unserviced car you'll invest money to keep it running to the price of the serviced cars
so, now you need new or low mileage alternator
you you should buy them until you get 13.8V while engine is running
same will be with automatic transmission, steering, suspension, air conditionion system....

Well aware I will have to invest money lol, that’s what I did when purchasing a brand new 350$ alternator. Which is new.


Very useful, thanks.

[ptpending]

there is no NEW alternator from BMW for E9X N52 N53 N51 for such a price
only refurbished by someone, or sometimes by Bosch itself
the NEW part from BMW 12317543083 (that means that it will have a regulator 100% compatible with particular e9x bsd bus) cost 800 USD without discount and around 500 USD with discount
so if you buy reman part you should double check if it is compatible
i share this because one year ago i pass thru this quest
my alternator began fail in tha way overvoltage and car began to disable ECUs after engine start
i brought car to service, and my indy mech ordered reman kit and regulator and we rebuilt alternator and replaced regulator on it
after that i missed one speed bump and all underhood content jumped and my alternator failed in another way, it simply stopped to charge car
so later i found the used low-mileage alternator, swapped it and finally battery charging stabilized
so from that i know that it is better to not rebuild alternator but search for used low-mileage or new one

[ctuna]

It might be worthwhile to check that the ground strap between the Engine in and chassis is not corroded and gone resistive. This is a common problem in cars with salted roads or corrosive atmoshere's (hot and humid).
The ground strap is generally below the starter motor.

[LegitRisk]

Originally Posted by ctuna

It might be worthwhile to check that the ground strap between the Engine in and chassis is not corroded and gone resistive. This is a common problem in cars with salted roads or corrosive atmoshere's (hot and humid).
The ground strap is generally below the starter motor.

Appreciate it, yeah I still have to do that yet. It could be a problem with that ground. I’ve discovered a few things lately that are telling me not all of the problems above are related so I’m trying to weed through the issues. From what I can tell there’s a random stutter when the voltage drops and it loses can communication.


I will check the strap and update, I will also fix the link for the PDF with my codes.

[LegitRisk]

Originally Posted by ptpending

there is no NEW alternator from BMW for E9X N52 N53 N51 for such a price
only refurbished by someone, or sometimes by Bosch itself
the NEW part from BMW 12317543083 (that means that it will have a regulator 100% compatible with particular e9x bsd bus) cost 800 USD without discount and around 500 USD with discount
so if you buy reman part you should double check if it is compatible
i share this because one year ago i pass thru this quest
my alternator began fail in tha way overvoltage and car began to disable ECUs after engine start
i brought car to service, and my indy mech ordered reman kit and regulator and we rebuilt alternator and replaced regulator on it
after that i missed one speed bump and all underhood content jumped and my alternator failed in another way, it simply stopped to charge car
so later i found the used low-mileage alternator, swapped it and finally battery charging stabilized
so from that i know that it is better to not rebuild alternator but search for used low-mileage or new one

Unfortunately this has been the case with 3 alternators, the one from on the car, a brand new one(the one that’s in, which is most certainly new), and a Bosche one from the junkyard and the symptoms have been better or worse based on the alternator, but not gone entirely which is why I think it’s **not** the alternator.

It doesn’t make any sense to be truthful.