I am chasing down the following code that comes back repeatedly from CAS after being cleared:

804092 Driver KL15N1: Short circuit to ground

I gather that KL15N1 is a "terminal" but I am not strongly familiar yet with what a "terminal" is in BMWspeak. Regardless, a link at bmwfault.codes has this to say (among other things):

1. Check connectors and lines between the control unit and KL15N1 partners for short circuit to ground.
2. Read out via the terminal status diagnostic command.

I'm guessing here that the control unit is the BDC. But what is KL15N1 specifically, and how do I identify what the "KL15N1 partners" are?

Chasing this down because I suspect it is causing a parasitic power drain affecting other systems, at least 2 of them major. Unfortunately, since the error does not identify a system, I'm left with what translates as "disconnect everything from the BDC and go from there," which is not exactly viable. Somehow I need to render this more specific.

Any informed guidance is appreciated. Thanks!

 

How about half informed guidance?

KL15N1 is an I/O port driver. If too many problems (short circuits) at this port are detected I believe the FEM (Front Electronics Module) turns the driver off: Shorts it to ground. This can't be undone. The fix requires the source of those short circuits be found and addressed and then whatever contains the KL15N1 I/O port driver, which may be the FEM, needs to be replaced.

 

Half informed is good, lol

I know the MINI FRM (FEM equivalent I guess) and its short circuit shutdown behavior well from having suffered that on my R56, which had a rear fog/reverse assembly filled with water when I bought it. That was fun. The folks at Way Motor Works were able to, uh, resurrect the circuit. I was happy its FRM didn't require replacement. Then at a later point, reconnecting the battery after some work fried the FRM (I'm sure you know about that whole boondoggle) and the resurrection was quite dead, requiring replacement of the unit. :facepalm:

The F56 doesn't have an FRM/FEM as such, they moved that functionality to the BDC. I use BimmerCode and the stuff I know is FRM/FEM under the R56 is in the BDC on the F56; there literally is no FEM shown in the list of modules when connecting with a tool to the F56. Also, I have no dead circuits so far as I know -- despite the fact that alongside the 804092 code I'm getting, I do in fact have another code saying "hey, I shut down a circuit permanently" from the BDC just as you describe ("8040B8: Driver KL30BKL15N: continuous deactivation due to short circuits to ground"). Which circuit it is deactivating, though, is anyone's guess, because all the lights and functions and blah blahs remain on and usable.

But I would -- for obvious reasons given that I am seeing both the 804092 and an 8040B8 -- like to chase down the source of the 804092, so that whatever it is doesn't get subjected to that perma-shutdown behavior and/lead my BDC to requiring replacement, and also so that it can stop screwing up the rest of the electronica in my car (previously mentioned parasitic power drain which, if real, is likely at least one root cause of other things I'm chasing around).

All that make sense?

 

Somewhat. I have been exposed to something similar to the above at least with other cars. But I had a good OBD2 diagnostics manual and a wiring diagram.

There is no FEM. But there is a BDC.

You pretty much stated what needs doing in your first post: "I'm guessing here that the control unit is the BDC. But what is KL15N1 specifically, and how do I identify what the "KL15N1 partners" are?"

You need a wiring diagram or documentation to know what circuit KL15N1 refers to. Knowing this then you would have a circuit to check

Also keep in mind it might not be a circuit but a fault in the BDC.

 

Ok -- this is coming together in my head -- and especially after re-reading what both of us wrote.

So -- KL15N1 is a terminal in the electrical sense, maybe even a physical point of contact, and based on what I have been able to dig up about KL15, a point of contact that provides +12V (or +5V, or +whatever V, but most likely +12V). It's not ground or some other-purposed something.

Courtesy of scrolling through the Realtime Values section of BimmerLink while connected to the car, I found out a few other key things:

- There are several KL15Nx terminals (at least 4).
- In monitoring the values, they will return either a 0 or a 1 indicating off (0) or on (1) status -- best as I can determine anyway. I mean, that makes sense.
- All the KL15Ns, including KL15N1, are returning status "1" while the engine is running.
- Since they are all power supply points, and I don't have a stack of electric-dead stuff in the car, the "1" presumably means "on" and the KL15N1, returning the same value as the other KL15Nx terminals, is therefore reasonably assumed to be very much live (this would also explain why nothing is dead on my car from terminal shutdown -- yet).

Looking back at the language "8040B8: Driver KL30BKL15N: continuous deactivation due to short circuits to ground" , I realize that it doesn't in fact come out and say permanent deactivation. I had assumed "continuous" meant "permanent" but if that assumption is incorrect, that would also explain why KL15N1 status is returning an "on" state despite the 8040B8.

• That doesn't mean the BDC isn't tracking a counter, though, just like the FRM/FEM -- and if it is tracking a counter, the BDC could eventually kill that terminal permanently as discussed.

It hadn't occurred to me that KL15N1 would show up quite literally as a labeled spot in a wiring diagram until now -- my brain was swimming in too many translation exercises, d'oh. I thought KL15N1 was some kind of logical KL15 (clearly a power terminal in my head) language-derivative or purpose-derivative or, well, you get the idea. But now I can go hunt for it.

Your last point -- the problem might be the BDC itself rather than a circuit downwind of KL15N1 -- um, yeah. Nasty possibility. Anytime something electrical is funky anything that is connected, including the endpoints themselves (can one even talk about an endpoint given that electricity in a circuit is a flow?), the whole lot is potentially a contributor to any trouble. We'll see what I find.

I do have two candidates for short circuit, separate from consulting wiring diagrams:

• one is a stranded-wire pair in the RF fender well, lashed to bare-metal frame with a ziptie (thanks BMW) and running to a ride height sensor attached to the RF control arm (it is used to guide headlight leveling).
  • While doing other work I found insulation on at least one of the wires compromised, and one of the conductors in that stranded wire kicked out/partially unbraided. I temporarily electrical-taped it up to avoid further damage and will be doing permanent repair (probably even tonight).
  • The wire pair is small enough that without pulling the wrapping around the pair back I can't tell if the second wire within is also compromised.
  • Though I'm going to repair this no matter what, I don't think it's the short to ground, as there has been no sign of trouble, whether codes or observable behavior, with the headlight leveling.
    
• the other is the AUC sensor. The BDC is consistently throwing two errors related to it, one of which may be a short, but note that the complaint about a possible short is a short to +V, not to ground. In any case I have a sensor on order.
  • 804398: AUC sensor: short circuit to positive or open circuit
  • 804399: AUC sensor: Invalid PWM signal (Reading I've done in Bimmerspace basically translates this as "sensor sending invalid values due to likely being electrictoast, get a new one", so that lines up.)

I'm off to find wiring diagrams and cross-reference all this stuff... we'll see what I find.

 

Ok, I'm on to some things.

From a few different sources turned up via Google search for:

• bmw "kl" meaning (include the quotes)

I've turned up that KL 15 = ignition position 2 ("accessory" - all electronics & modules re powered). Here's a good/example explanatory link.

From wiring diagrams I've sussed out:

• KL15N1 -- or more accurately, KL15N_1 -- connects the front power distribution box to the BDC, and does so via connector A258*3B, pin 20.
• Connector A258*3B carries... a lot of stuff. A *whole* lot of stuff.
• Included in "stuff" is one ground-side path (pin 27) for the AUC sensor.
• Included in "stuff" is also pins 20 and 24, the per-BMW/MINI-instruction splice-in points for the MINI Click & Drive system on my car.
  • Note that A258*3B, pin 20 is the +12V feed from the front power distribution box to the BDC. So that's why BMW/MINI picked that wire. GAH come on...

I followed factory instruction when installing that MINI Click & Drive system, so I know exactly what was done and where:

• Might be a problem with the wire. I was not fond of those kit-supplied splices at all and despite BMW/MINI instruction, the space really was not made to have splices put there in the first place. It's just too cramped and, well, you get the idea.
• Might be a problem with the cigarette lighter adapter that is part of the circuit.
  • The two wires go to a female adapter socket, within which is installed a BMW USB-A cigarette lighter charger, part 65412458284.
  • A plastic bracket plus ziptie hold the socket and cigarette lighter charger together.
    • I have no idea whether any of the external metal cladding on the charge and/or socket could provide a path to ground if touching nearby metal. But guessing "yes" for at least some part of it.
  • Plugged into the charger is a USB-A male to female extension cable (whose female end is what you plug things into on the Click & Drive main unit). Pretty much nothing but plastic (except for the intended parts of the cable ends, of course)

Also thinking the "KL30BKL15N" means something is up involving both terminals KL30B and KL15N.

More to look at tonight I guess, but if I had to bet ten bucks right now, I'd say my "short" is the Click & Drive system, and the way to find out for sure is to physically disconnect its path to ground.

 

Re Click and Drive system... Last thing touched is first thing suspected. Crimp connections can be good or bad. Over the years I have once (well, ok twice) found after crimping two wire ends together and giving the wires a tug a wire comes out.

But solder may not be the answer. In some sensor circuits solder changes the resistance and can affect the readings. For example I was told to *not* use solder to connect OEM O2 sensors to the old sensors' wiring leads. I bought some fancy crimp connectors which had some kind of goo in them that upon crimping would release the goo and seal the crimp.

They worked ok and passed the tug test. But next time I needed to replace O2 sensors I just bought the factory sensors with the connectors on the sensor wiring leads.

 

I hear you on all points.

I didn't get into the car last night because I was up WAY late digging up wiring info, info on the terminals, and info on the Car Access System (CAS) that all this error noise is happening under. Learned a LOT and decided to go to bed to let it cook and sort in my head.

That was a good call, because I think I know why I don't have a circuit permanently shut down (assuming the Click & Drive is the problem, which I'll firmly confirm yay/nay on today). With the Click & Drive system installed, there isn't a circuit you can shut down without seriously messing up the car.

• The +12V side that is tapped into -- which is in fact KL 15N_1 -- comes from the front power distribution box. Not gonna turn that box off, ever, even if there is a way for the computer to dynamically do so. That would be bad. The scope of power loss would be huge. Heck, you might not even be able to drive the car as a practical matter in such scenario.
• The other side of that +12V tapped-into wire is the BDC. Turn that off? Yeahno, unless you want to turn off what looks like at least 10 different circuits that the BDC uses that particular feed to power (fuses F49 - F60, with some gaps).

So I may have gotten lucky here, though there is a clear imperative to get to the bottom of this before some kind of BDC-protection logic kicks in.

On to your comments about splicing, well, yeah. The irony here is that I bought the Click & Drive specifically because it was a Genuine MINI Accessory. I was new to the F56 and having learned some things in my R56, I wasn't going near an aftermarket product requiring a power tap, and I needed a power tap for charging (I put an iOttie cradle on my Click & Drive that does Qi charging and auto open/close -- very cool). Fast forward to today. If I knew then what I know now -- that the directive was to tap a power feed to the BDC itself -- there is no way I would dare tap it. Absolutely not. Regular vibration of the car alone makes that a giant "you're asking for it, buddy." No no no no no. NO way. I would have decided that BMW/MINI had lost its mind, and I would have done something better and safer.

I don't know, btw, if you've ever seen the wires I'm talking about, but A258 is a 54-pin connector and its wires (including the ones under discussion) are a mere 0.5mm. Fricking tiny. Splicing into something that small -- again -- is asking for trouble. I only went with it at the time because if the manufacturer says do that it's ok and even the right thing to do that, right? Ehhhhhh...

More to come

 

Oh, and the ground side of the Click & Drive spliced into A258 pin 24? That wire is 0.35mm and is the ground side of the refrigerant pressure sensor (as in AC). I'm sure there's some logic to picking that one, but what that logic is... is beyond me.

 

Think you are well on the way to getting this sorted out. Good job sticking to it.

 

Thanks! And... I have an update.

I haven't dug in at the splice point yet, but since what is spliced in is a 2-conductor wire leading to a cigarette lighter/accessory socket to plug in a cigarette lighter USB, I figured I could kill off the electrical path by yanking the cig liter USB. That tactic would work if the short were through the cig lighter USB itself, rather than back at the splice points.

And prelim results are...

• Instead of getting wonky up/down charging/depleting of the battery while driving, the battery is being charged almost 100% of the time. Things are WAY better now. The obvious implication is that the short was real and it was vacuuming up enough alternator and battery output to screw up the expected behaviors/etc of both.
• The 804092 does not appear to be returning (I cleared the code first). Prior to this tinkering, it would always return at next start after clearing the code.
• The 8040B8 is still around (won't clear), but that isn't exactly a surprise.
  • I did find another reference (in BimmerLink itself) referring to this as the permanent circuit shutdown we were discussing (even though I clearly don't have a circuit shut down -- or at least not one that affects anything in obvious use).
  • BimmerLink can't clear it and my Foxwell NT710 can't clear it. There is a "reset module" option in the Foxwell but I'm digging around to get clarity on what that does in full before hitting the button.
  • I've sort of figured out what ISTA is (don't laugh at me everyone, lol) and may just add that to the mix before making any real attempt to make the 8040B8 go away.

I have a hunch based on my observations while chasing charging problems that there is a temperature-driven variable here, which would almost definitely point back at the splice points being a problem no matter what. So going to pull the trim and scrutinize in a couple of hours.

W00t! Progress! More to come

 

Update - popped the panel covering the A258*3B. Didn't find much of a smoking gun, which was a surprise.

• Back in 2021 when I installed the Click & Drive thing I apparently anticipated vibration and the like, and made sure cabling and connectors were secured pretty well. They aren't flopping around. They're solidly in place.
• +12V to its inline accessory/cigarette lighter socket is confirmed as coming from a splice into a Black/Green wire on pin 20 (which, as previously noted, runs between the front power distribution box, and is terminal (aka KL) 15N_1).
  • Though the Click & Drive instructions (circa 2013) indicate pin 20 should is connected to a Green/Gray wire, diagrams of the vehicle (circa 2019+) show that the pin 20 wire can be either Green/Gray or Black/Green (presumably depending on production date).
• GND to its inline accessory/cigarette lighter socket is confirmed as supplied via a splice into a Brown/Black wire on pin 24 (which runs between the BDC and the refrigerant pressure sensor).
• Again, the connections to both pin 20 and pin 24 are as per the Click & Drive installation instructions. So the odd choices are BMW's rather than mine.
  • Despite the odd splice-in choices, the real issue here could be the USB adapter or the upstream iOttie having an internal short.
  • Both of those possibilities highlight -- to me at least -- that a better option for powering this doodad is to run something off the bone stock front accessory outlet circuit. At least the car (wiring and computer systems alike), from a factory design standpoint, expects things like a wonky plug-in USB charging device to be there (vs. +12V from electrical parallel with the BDC, with ground then supplied via a BDC-controlled HVAC control circuit. )
• The AUC sensor-related complaints (short either to B+ or open circuit) are gone and not returning. Still observing on this one, but it may mean that the sensor was fine but power-deprived.

Despite being a bit concerned about the physical interaction between the splice connectors and the A258*B3 wires, I'm even more concerned about doing damage to the factory harness by removing them. So for now I think I'm going to leave the A258*B3 end hooked up, and leave the Click & Drive accessory/cigarette lighter socket tucked away and empty.

At some point -- maybe after a week or two of driving -- whenever I'm convinced that the 804092 is 100% dead, I'll probably snip and cap the wires near the socket end, which should remove any "future possible curiosities."

Next thing for me to do is figure out how to deal with the 8040B8. I've found a 2019 thread at Bimmerpost about resetting the short circuit counter, and an older (2015) howto against the FRM over at Bimmerfest. Both call for the use of Tool32, which I have seen referenced in a few places but have no hands-on with. Off to the rabbit hole to learn about Tool32 and get what I need to use it on this situation.

More to come. @RockC I really appreciate your help with this. Huge help. I owe you one.

 

You're welcome. And you don't owe me anything. Really I just sought to give you a nudge. If you get the opportunity pay whatever you can forward. You're the expert on this 804092 / KL15N1 FRM/BDC business now.

Have a Happy New Year!

 

Quick update (and final for a while, until I get get Tool32 up and running to deal with the 8040B8). None of the following have returned:

- The 804092 Driver KL15N1: Short circuit to ground
- The many and varied info-tier and error-tier complaints (viewable only with a scan tool of whatever kind) about various modules not successfully talking with other modules, sometimes in critical ways.
- The intermittent non-presence of electric power steering at engine start.
- Really crappy charging of the battery (to the point of undercharging) by the vehicle when running.
- Parasitic battery drain while not running.

Good stuff. As for the 8040B8, given that everything in the car seems to be running, its import is unclear. But I can't get near it without getting Tool32 running, so going to be a bit.

 

Quick and final update -- got rid of the last remaining code, the 8040B8:

- Did *not* need Tool32 and the techniques floating around the net to clear similar codes where the BDC (or in prior incarnations, the FRM) permanently shuts down a light bulb due to repeated short circuit.
- ISTA+ was able to do the trick.
- It kept reappearing because the "Is currently present" status of the code was "Yes".
- Clearing that status was something ISTA+ was capable of doing, just by using its test plan function on the fault code.
- Once that status was cleared, it was possible to clear the code itself.

Have test driven, it's been more than half a day now, this baby is taken care of. FINALLY. Thank you to literally everyone who participated in my various figure-out-my-electrical-woes threads, hopefully I can return the favor with all the junk I've acquired in my head in the process of learning how it all worked