[Ikejones]

Hey guy, this past sunday i woke up to a flat battery. Tried to jump start the car using the posts in the engine bay, but ended up removing it and bringing it to the auto store nearby to charge. They charged and said the battery was good. Put it in the car and cranked like a champ. Thought all was fine, Now for the past 3 days, I have been getting intermittent issues, ranging from not too bad to really shitty.

I have a jb4. Ever since the flat battery, whenever the jb4 is enabled in any mode other than 0(disabled), the gauge cluster will randomly go crazy. Works fine, then suddenly the needles jumps to the far side or moves back and forth. Then it goes back to working. Randomly occurs. I found by turning on the car and having the jb4 disabled, this issue is not experienced. I have already reflashed the jb4 with a later firmware, but it didnt make a difference. I would say its fried, but the fact that i can interface with it via pc and using the steering wheel makes me think differently.

Sometimes while driving i get the CEL warning for engine malfunction, reduced power. Sometimes it occurs quickly,other times it doesnt occur. Drove for 30 minutes each way today for work. Didnt experience on the way, but did on the way home around the 28 minute mark. Wasnt driving hard at all. When i run the codes, i see the code 2f4a and 29f1. Read on another forum that 2f4a means "Your ECU and immobilser have become unsynced.", but it didnt include a fix.

I also now have a brake light switch circuit malfunction, even though the brake lights work. Online it looks like thats a 40 dollar fix, so not bad. Its the least of my concerns, although I have a hard time believing that sensor just happened to go bad when all the other stuff is going on, unless the battery going flat shorted it.

My Comfort Access is not working as well as usual. Still dont have to put in a key, but i cant just walk up to my door and pull the handle anymore. I have to manually push the button on the fob. Not a huge deal, but i already miss it.

Any idea what might be my fix, before I drop her off at a shop? Iv used solo motorsports in Norcross Ga in the past, so i will probably bring to them if needed, but im not as close anymore, so a home fix would be preferable.

List of codes pulled
Tonight - I think the root cause is going to be the 2f4a code.
2f63- Brake light switch, plausibility
2f64- No Description found
29f1- Fuel pressure, plausibility
2f4a- Interface EWS-DME electronic vehicle immobilisation/digital motor electronics

Last night- 3 codes pulls, dont remember the order. pulling from screenshots. Not that concerned about the low boost and fuel pressure, as the car acted kinda funny a few times after disconnecting from the jb4 or enabling/disabling it. Went away immediately after the next crank
Code pull 1
2f64- No Description Found
2f63- Brake light switch, plausibility
2f4a- Interface EWS-DME electronic vehicle immobilization/digital motor electronics
29f1- Fuel pressure, plausibility

2f64- No Description Found
2f63- Brake light switch, plausibility
2fbe- Fuel pressure after motor stop
29f1- fuel pressure, plausibility

3100- low boost mode engaged --CEL displayed
2f63- Brake light switch, plausibility
2f64- No Description Found
2fb3- fuel pressure after motor stop

Thanks in advance for all your help and comments.

Jeremy

[jt335i]

Hmm. Maybe the alternator might be on it's last leg. Try having that checked.

[Nitrousbird]

Sounds like a bad alternator to me.

[Ikejones]

hmm, was hoping i wouldnt hear something like that, but ill have to get it checked out then. Drove it this morning, no issues.

Do you say bad alternator because its like the power is fluctuating, which is what causes codes to be thrown when under a load? Which i guess would make sense for why the jb4 is having issues, since as soon as its out of mode 0 it puts that additional load on the engine when more boost is applied.

I'm at work so cant spend much time looking right now, but is that a pretty expensive job on the 335i? I can do small stuff no problem, but i tend to stay away from the bigger jobs since its my main means of transportation. Iv got a neighbor thats a mechanic who i might be able to pay to help me, but since he does that all day, not sure how much he will want to do that after hours.

[jt335i]

At first, I thought it might be that one of your battery cells is dying, but I recently had the batt replaced on my 335 after receiving the "Increase battery discarge" message on my iDrive. Even if I tried to charge it, it would still say that the battery voltage is good so that's when I took it to my indy mechanic and he found that the one of the cells is bad. If you're iDrive is not giving you that message or something similar like "Increased battery discharge when stationary. Electrical consumers were temporarily switched off." then your battery is still good as what the auto store says and therefore it has to be your alternator or something related to it.

As far as cost to replace an alernator, that's tough to gauge since every shop (whether it's an indy, chain, or dealer) is different so you'd have to call around to get a quote or estimate. Of course, there's the DIY approach or, like you said, your neighbor mechanic who can help, but does he know a lot about BMWs. Anyway, good luck and hope you get this issue fixed.

[Ikejones]

i havent had any battery messages, so im confident that the battery is good. I called around and labor doesnt sound too bad, about 300 bucks plus parts.

Kinda hoping it magically disappears if i drive for a little bit with the jb4 off. Ill probably check with the neighbor or bring it in soon though. Thanks for your input.

[Ikejones]

Tested my alternator last night and it doesnt appear to have an issue. I just enabled the voltage readout in the hidden menu and took it for a spin. Ran 14.1-14.3 pretty consistently while driving. No issues experienced. I turned on my jb4 to map 1 after that and still didnt have any issues. Same voltage. That was only for a quick 15-20 minute drive though, so not sure if that really counts. Guage issue when chip was enabled typically occured within a few minutes though, so its somewhat of a good sign.

Replaced the batteries in my fobs, hoping maybe they were just too low for confort access to pickup from outside the car, but no such luck. CA only works for starting the car and opening the trunk. Unlocking by pulling door handles is still a dud.

[SSSnakeman]

How did this turn out? I had a bad battery and still have this 2f4a code after replacement.

[Miller335]

Originally Posted by sappy13

i havent had any battery messages, so im confident that the battery is good. I called around and labor doesnt sound too bad, about 300 bucks plus parts.

Kinda hoping it magically disappears if i drive for a little bit with the jb4 off. Ill probably check with the neighbor or bring it in soon though. Thanks for your input.

Just because you're not getting warnings doesn't mean the battery isn't bad.
Just because the auto parts store said the battery was good doesn't mean it is either.

I just dealt with this yesterday, everything checked out but my battery was dead. Swapped the battery, reset the IBS and now all is good.