[samspiderman3125]

2017 440i Gran coupe F36 8AT

Wanted to document this for anyone else, as I've seen others with battery draw issues, but nobody really listing much info in one place.

After doing extensive research and dealing with this issue on my own vehicle, i finally found the answers to some weird battery draws people have had over the years

Culprit 1: comfort access door handles, these are known to go bad a lot and cause a draw on the battery.... easy ways to check include pulling the fuse for telematics and comfort access in the FEM module, or using a pyrometer to check for any door handles hotter than others. MOST COMMON issue

Culprit 2: bad telematics module, rare, but have heard of a few having issues with this drawing, usually happens if a vehicle has been wrapped, repaired, or the top of the shark fin on the roof of the car has been messed with, this leads to slight water intrusion and shorting of the telematics module, you can also pull the fuse in the FEM to find this, same fuse as the comfort door handles for the F36(idk others)

Culprit 3: OBD devices, usb devices, or cigarette lighter plugins... you'd think by now bmw could make a car that could sense current draw on external devices and shut them off, but whatever, these can cause the FEM unit to stay awake and draw power

Culprit 4: FEM module itself, although rare, some of the earlier f series had water intrusion issues that would cause an internal short and cause the FEM to stay awake, although i believe most of these have been replaced by now, still possible, check for dried water drip lines in the passenger side kick panel and corrosion in FEM fuses.

Culprit 5: bad cluster. I feel this one is one of the most important failures to document in here, as i have only seen 2-3 threads on this and most was speculation. I am writing this from the perspective of someone who has had this issue and diagnosed it myself with cold hard facts lol.... the 6wa cluster is the only one I've seen do this, but I'm sure the 6wb could do it as well. One of the know culprits of WHY this happens is a previously shorted/failed ambient temp sensor, no clue why... but sometimes will fry the instrument cluster in a way that causes the car to stay awake. DOCUMENTED symptoms include, backlighting on push to start button staying on, and while you can only see it at night, the lcd backlighting for the instrument cluster will stay lit, you can see lighting from the "black" pixels. To diagnose, unplug instrument cluster only! lock car and set a timer for 30min, some people say 16 min is all it takes for the car to shut off, some say 20, so 30min is a safe number. If after locking the vehicle and unplugging the cluster you see your backlighting on your push to start button turn off, its 99% sure your instrument cluster. 6wb cluster retrofit will fix this issue if someone is wanting to upgrade at this time too. For some reason others have had issues with cloned clusters still drawing even on a new unit.

Culprit 6?: only have seen in one random thread in reddit, but some have expirnced draws because of improperly repaired headlight wiring, idk the details on that... but its possible

Note: your ambient temp sensor can be reading and accurate and you can still have a cluster issue.

as always, if anyone has any questions or needs and advice, feel free to contact me

[SSer61705]

Thanks for all of these, as from the other thread you can see I'm headed down the same rabbit hole. Eventually we can consolidate . Doesn't seem too entirely rare as there are several threads on it and outside this forum many references as well. All indications for me are this is a crazy intermittent issue. Every 2-4 weeks, a big drain. Sorry about duplicating here, but going through these to give my state in this thread. Also, I added a couple more potential culprits

Culprit 1: Not out of the question. Thermal camera would be a good check, not sure where I can score one from for reasonable or borrow. Have to look into it.

Culprit 2: Can't rule out, but unlikely. Problem again is intermittency. It has to go into the bad state the pull fuse and confirm. I have yet to actively find it in a bad state with a clamp meter on negative terminal (admittedly not the best one, but I've worked it out I think)

Culprit 3: possible from bad USB charger cable (apple with ubiquitous bad end by lightening connector) Though I can't say for certain this didn't happen without it plugged in, I just know it didn't happen the last time until i left it plugged. But that a lot of juice to draw overnight through that.

Culprit 4: No idea, again, intermittency. Would this throw codes? If so, what?

Culprit 5: I keep coming back to this but have no definitive diagnosis. S/S button does not stay lit (unless again, intermittent and haven't caught it) Was this a continuous condition for you?)

Culprit 6: No reason to think this.

I'll add 2

Culprit 7: Puddle lights: aftermarket puddle lights for pretty roundel projection. They can apparently go bad and cause this. Just took mine out entirely. This was after the last episode, so who's to say.

Culprit 8: Aux Electric coolant pump. Some have had this go haywire too. Mostly just comes on and runs til battery drains. I believe on occasion there have been some "cycling" situations where it goes on/off until battery drains. The issue for me is I don't drive this thing hard. I had it come on once after idling in driveway (why would turbo/intc be hot enough to draw that) and it ran for a few minutes and then shut off. I wasn't familiar enough with this to let it sit and see if it started to cycle. Assumed it was normal. Problem is, it has never come on again since. Whether idling in drive or driving for while or anything. It really raises the question of why it came on in the driveway. So this is still on the table. Seeing if I can get it to do it again and just let it go and see if it drains the batt.

FUN!

[samspiderman3125]

Originally Posted by SSer61705

Thanks for all of these, as from the other thread you can see I'm headed down the same rabbit hole. Eventually we can consolidate . Doesn't seem too entirely rare as there are several threads on it and outside this forum many references as well. All indications for me are this is a crazy intermittent issue. Every 2-4 weeks, a big drain. Sorry about duplicating here, but going through these to give my state in this thread. Also, I added a couple more potential culprits

Culprit 1: Not out of the question. Thermal camera would be a good check, not sure where I can score one from for reasonable or borrow. Have to look into it.

Culprit 2: Can't rule out, but unlikely. Problem again is intermittency. It has to go into the bad state the pull fuse and confirm. I have yet to actively find it in a bad state with a clamp meter on negative terminal (admittedly not the best one, but I've worked it out I think)

Culprit 3: possible from bad USB charger cable (apple with ubiquitous bad end by lightening connector) Though I can't say for certain this didn't happen without it plugged in, I just know it didn't happen the last time until i left it plugged. But that a lot of juice to draw overnight through that.

Culprit 4: No idea, again, intermittency. Would this throw codes? If so, what?

Culprit 5: I keep coming back to this but have no definitive diagnosis. S/S button does not stay lit (unless again, intermittent and haven't caught it) Was this a continuous condition for you?)

Culprit 6: No reason to think this.

I'll add 2

Culprit 7: Puddle lights: aftermarket puddle lights for pretty roundel projection. They can apparently go bad and cause this. Just took mine out entirely. This was after the last episode, so who's to say.

Culprit 8: Aux Electric coolant pump. Some have had this go haywire too. Mostly just comes on and runs til battery drains. I believe on occasion there have been some "cycling" situations where it goes on/off until battery drains. The issue for me is I don't drive this thing hard. I had it come on once after idling in driveway (why would turbo/intc be hot enough to draw that) and it ran for a few minutes and then shut off. I wasn't familiar enough with this to let it sit and see if it started to cycle. Assumed it was normal. Problem is, it has never come on again since. Whether idling in drive or driving for while or anything. It really raises the question of why it came on in the driveway. So this is still on the table. Seeing if I can get it to do it again and just let it go and see if it drains the batt.

FUN!

Thanks for adding man! i hope to see others add to it so we can all have some sort of checklist for this BS

PS: thermal camera https://www.thermoworks.com/ir-gun/?...BoCEOgQAvD_BwE