[goblinslop]

I have been chasing a ridiculous electrical issue on my 2007 335i sedan for quite some time now. It first started when the car died suddenly while driving and had to be jump started. I first replaced the voltage regulator and then the battery with no luck. I also measured the output of the alternator directly from its positive terminal and it put out a steady 13.8v at idle. I then checked the grounds and cleaned most of the connections on the B+ circuit in the engine bay, both to no avail. I checked parasitic draw, and had it measure over 8amps, leading me believe I was finally getting somewhere. As is recommended, I let the car fully sleep and began pulling fused one by one, but every fuse I pulled seemed to lower the parasitic draw a tiny bit. The draw falls to around 3 amps when I pull the CAS, footwell module, and B+ potential distributor fuses, but that is as low as I have gotten it to go. I would greatly appreciate any insight or advice on this issue.

[GoRomeo]

Originally Posted by goblinslop

I have been chasing a ridiculous electrical issue on my 2007 335i sedan for quite some time now. It first started when the car died suddenly while driving and had to be jump started. I first replaced the voltage regulator and then the battery with no luck. I also measured the output of the alternator directly from its positive terminal and it put out a steady 13.8v at idle. I then checked the grounds and cleaned most of the connections on the B+ circuit in the engine bay, both to no avail. I checked parasitic draw, and had it measure over 8amps, leading me believe I was finally getting somewhere. As is recommended, I let the car fully sleep and began pulling fused one by one, but every fuse I pulled seemed to lower the parasitic draw a tiny bit. The draw falls to around 3 amps when I pull the CAS, footwell module, and B+ potential distributor fuses, but that is as low as I have gotten it to go. I would greatly appreciate any insight or advice on this issue.

I wonder what led you to replace the voltage regulator and battery? Did you read fault codes when this happened?

[Frozz]

I had this same issue, my issue was the JBE body control module under the fuse box. You must remove the glove box and find it under the fuse panel. You'll need a Torx, Phillips screwdriver, and small hands. Make sure when you pull yours that you note "JFBBFE III", "JFBBFE II" or "JFBBFE I" as you will need to match the replacement. They can be found on eBay for about $50. I'd also keep an eye on that alternator voltage as it could be overvolting intermittently(which was the cause of my JBE failure).

Also, are you sure the car is fully sleeping? Full sleep would make the gear selector indicator light turn off.

[goblinslop]

GoRomeo, I replaced the VR and battery because I was being dumb and throwing parts at my car. I read the fault codes through mhd and got a generator code, which led me to test the alternator (after already having replaced the VR) and determine that it is working fine. Frozz, I am almost positive the car is fully sleeping as the gear selector indicator light does turn off. I have been testing the parasitic draw by tricking the passenger door and trunk into thinking they are closed, letting the car sleep, and then removing the negative battery cable and testing for parasitic draw at the battery while pulling fuses. Could I somehow be triggering the car to wake when I connect the multimeter? Is there any way I could test to see if my JBE body control module is working before I outright replace it?

[goblinslop]

I performed a voltage drop test across every single fuse after letting the car sleep. To my surprise I found absolutely no voltage drop anywhere. I suppose that I had been accidentally triggering the car to wake on my previous testing attempts, so perhaps I don't have a parasitic draw after all. At this point I am truly baffled as to why my battery is discharging. Like I mentioned before, I tested the alternator directly on its positive terminal and had it read 13.8v on my multimeter (while my secret menu readout was showing 13.5v). When I am driving the car, the dash readout would not give me anything over 14v (which I figured was actually about 14.3v), which does seem somewhat low but not unbelievably so. Could my alternator be just weak enough to cause the car to die while driving? I had parked the car and measured the battery voltage at 12.6v just after turning it off, but came back the next morning and measured it at 10.8v, which led me to my parasitic draw conclusion.

[Frozz]

I think at the point you're at currently, trying the JBE swap wouldn't hurt. It's a relatively quick swap, and if it does not fix your issue, they're pretty quick to re-sell on eBay or find a seller that allows returns.

[ptpending]

you should consider not jbe swap, but junction box positive cable plug replacement
thats the reason why car suddenly lose all electric power

[nfiftyfourgasm]

Any updates?
I have a relatable issue, car wouldn’t start unless jumped even though the battery was good, ended up being the positive cable ends in the trunk that go into the body from the battery well were corroded from water, new positive cable did the trick for me. To verify the issue I tested for continuity from the positive terminal on the battery up to the positive jump point at the front of the car next to the dme box. I saw I didn’t have continuity, that’s when I took off the battery and removed the positive battery cable that attached to the battery and to the body wire in the trunk that runs up to the front of the car, I then tested the point where the positive cable attached to the body wire (stud in the battery well) up to the positive jump point to the front and I had continuity. So that isolated my problem to being the positive battery cable. With the positive battery cable completely removed I tested it for continuity and had nothing. A good one should have continuity with less than 1 ohm of resistance. Put in a new one and she started right up. It makes sense that my car would only start when jumped because voltage was being supplied at the front directly to the dme and didn’t have to go through the bad positive battery cable.

[ctuna]

There was a recall on some model years for the Power connection to the Cabin Fuse Box being bad. The symptom was all the power to dash going out and the motor stoppin I believe.

https://www.e90post.com/forums/showthread.php?t=820317