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      01-10-2021, 12:12 AM   #1
Purple Tom
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F25 Heated Seat Problem

Hi,

Iím after a bit of advice if possible. I bought a 2011 F25 x20d on the 27/12/20. I knew it had some issues but it was cheap and I like a project. One of the main things was that the heated seats didnít work - the three stage switches for the front seats lit up as usual but there was no heat and the rear heated seat switches didnít light up when pressed and had no illumination to them either.

I bought the car anyway and on the drive home, after about 20 minutes of driving, the front heated seats suddenly came to life. I could hear a clicking from under the dash somewhere when I pressed the switches and there was heat to both seats. I couldnít however tell if the rear seats were working. The car had been stood for a couple of months so I put the problem down to a low battery and thought nothing more of it.

Iíve been doing some other stuff to the car in my workshop and itís now back on the road, however the seats have stopped working again. Iíve changed the battery and done the battery learn procedure so itís definitely not related to that. I have a Foxwell NT530 so I scanned the car last night and in the JBBF it threw up the following fault codes:

C90D71 - Seat heating, rear passengers side, missing LIN component

C90D72 - Seat heating, drivers side rear, missing LIN component

C90D73 - Seat heating switch, rear drivers side, missing LIN component

C90D74 - AUC Sensor: does not respond

C90D83 - Seat heating switch, rear passengers side, missing LIN component

C90D9B - Seat heating, passenger: no LIN component

C90D9C - Seat heating, driver: no LIN component

Iím a little stumped on this - Iím used to slightly older cars without LINBUS and despite some research Iím not even sure what a LIN component is. From what I can tell it means some issue somewhere with the LIN for the heated seats, but the fact that they worked briefly on the way home would suggest that physically the seats are ok, it could be more of a wiring issue somewhere...

Can anyone advise or offer any assistance? Sorry for the long post.

Thanks
Tom
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      01-12-2021, 09:09 AM   #2
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In for responses

I had the same issue, all heated seats stopped working except driver's side but the buttons still lit up. Then a couple weeks ago the GF tried them after I said they'd been broken for years and bam... they worked. I'd originally assumed the module was bad but perhaps it's one of the systems the ecu cute power to when low voltage is detected?
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      01-16-2021, 11:37 AM   #3
Purple Tom
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I initially thought it was voltage related, but a new battery and the battery code procedure didnít solve the problem.

They randomly worked again for half an hour a couple of days ago. I turned the engine and ignition off, left the car for a few minutes then came back to it and they werenít working again.

Very odd. Can anyone assist with a bit more of an idea as to what a LIN component is? Is it the module itself?
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      04-26-2021, 04:16 PM   #4
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I have exactly the same problem and it is not intermittent. It is permanent. Still researching. I have not been able to find any useful information to solve this problem.

Last edited by mineralfarmer; 04-26-2021 at 04:32 PM..
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      10-05-2021, 01:28 PM   #5
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Talking Same mysterious problem!

I have a 2014 X3 (F25) and have the same exact issue. Back in 2019, the passenger, rear R & L seats lost heating function.
Issue:
The front drive works just fine button and heat wise The front passenger button lights up with the 3 stage LEDs but no heat and the ISTA+ registers the button presses. All 3 throw an error code with the LIN - Missing heating module and the recirculatory sensor AUC or something like that.

What I've done so far:
I checked the 4 20A fuses in the rear Fbox and the 5A one in the front Fbox and all is well there, there is also 14V at the power connector on each module. I purchased 2 used heating modules and tried to replace the front and rear ones with no luck, which leads me to think that the issue is somewhere on the LIN between the modules and JBE or chassis electronics (see attached image). That JBE module is attached to the fuse junction box behind the glovebox and it all makes sense until you realize that this module manages many different things like parking sensors, window motors, and so on.

If anyone out there has figured this fault our or knows how to test the yellow data wire without an oscilloscope, that would be a huge help.
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      01-02-2022, 08:54 PM   #6
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Same problem. 2013. Right front and both rears do not heat up. Missing LIN component. Will try to get in with the dealer this week and see if they can diagnose.
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      01-03-2022, 10:09 AM   #7
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Basically the AUC sensor is an air quality sensor. It's located under the hood by the cabin air filter. It's job is to provide air quality information to the HVAC system. The HVAC system will switch to recirc automatically if it detects bad air quality.

LIN stands roughly for Local Information Network and is one of the car's communication busses. I'm guessing the various components aren't talking/responding on the LIN bus. As the fault occurs on multiple locations, I'd be looking at common components to all of them.

For whatever reason, the AUC LIN wire is on the same sub-circuit as the rear seat heaters.
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      01-03-2022, 10:38 AM   #8
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For the rear heated seats, the LIN circuit for the two heating modules, the two switches, and the AUC sensor are all tied together and terminate at pin 1B-9 of the junction box.

Front seat heating modules are also connected to the LIN bus. However there's also a Driver's Seat Module that also appears to control the driver's seat heating and does not connect to the LIN bus. I doubt they both exist in any given car, but it might explain why driver's is not failing. As the front switches are integrated into the HVAC controls, there's not a direct LIN bus connection.
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      01-05-2022, 07:29 PM   #9
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From Bmw fault codes:

Check voltage supply of seat heating module.
Check the connection between JBE and seat heating electronics (LIN-bus).
Check seat heating module.
Check if JBE is encoded.
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      01-16-2022, 09:20 PM   #10
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I have "C90D71: Seating heating, rear passenger's side: missing LIN component" and "C90D72: Seat heating, driver's side, rear: missing LIN component." Can we get to the bottom of this?

I've had my LCI F25 28i since 2019, purchased it essentially new with 7,000 miles on it. There were a couple times back in 2019 when I switched the rear heat seating on "just because" and I remember thinking when I felt the seats "it doesn't feel like the seats are heating." I forgot about it because I never sit in the rear and no one else does either. Fast forward to 2022, when I took my X3 to the dealer to take care of an emissions recall, they updated my I-Level and when I received the paperwork, they noted the above errors stating they were present before+afterwards the update. I also see the errors with ISTA-D on my computer. The issue is definitely not vehicle software related. I do have a warranty on my car, so I would think the issue should be fixed and covered, but I am of course looking to determine the problem myself. Very strange issue. I have installed a radar and added subwoofer, but I know none of the work I have done is related to the heating issues.
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      01-17-2022, 05:31 PM   #11
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My right rear heated seat isn't working and I'll just add my experience here in case it helps anyone. The switch doesn't light up and nothing happens when I press the button. First thing I did was check the fuses, all of them were good. So then I took off the switch panel and noticed a fair amount of corrosion near the connecters of both the left and right switch modules. I removed the circuit board from each switch housing and cleaned off all the corrosion with rubbing alcohol and an old toothbrush. While cleaning them I noticed that it looked like one of the SMT transistors on the right side switch was burnt out, the marking on it was "5CW", about the size of a grain of rice. Doing some digging it looks like its a pretty standard PNP switching transistor so I ordered a handful off digikey (link below). I haven't received them yet, but when I do I'll solder it up and update the thread here.

I'm not sure what could have caused corrosion like that, it almost looked like an alkaline battery when they die, but there's no battery in the switch modules. Maybe previous owner spilled something and the current over time caused it, hard to say.

Transistor part: https://www.digikey.com/en/products/...40-235/1232236
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      01-19-2022, 01:10 PM   #12
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As it turns out, on my last trip to Albuquerque I didn't have time to go to the dealer to have this problem diagnosed or fixed. I'm 6 hours away from any dealer at all, so based on some other posts on the web I ordered a new seat heat module and replaced the one underneath the front passenger seat to start with. It had no effect. Whatever it is it's the same problem the folks above have. Front passenger seat button lights up but no heat. Rear seat buttons don't even light up.
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      01-19-2022, 07:53 PM   #13
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Quote:
Originally Posted by mineralfarmer View Post
What is the j b e and where would this connection between the jbe and the eating Electronics be?
The front heated seats aren't connected using LIN, but the rear ones are. The JBE is attached to the glovebox fuse panel and the yellow lines in the diagram are the LIN connection to the rear seat heating electronics.
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      01-20-2022, 09:00 AM   #14
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Thank you for providing this. I still don't know if the actual wire I'm looking for is yellow or if it's just yellow in the diagram. And regardless, it seems unlikely that there is a broken wire. I suspect this is more of a computer programming or coding issue and the remote advice that I got from a dealer was along these same lines.
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      01-20-2022, 01:04 PM   #15
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Quote:
Originally Posted by mineralfarmer View Post
Thank you for providing this. I still don't know if the actual wire I'm looking for is yellow or if it's just yellow in the diagram. And regardless, it seems unlikely that there is a broken wire. I suspect this is more of a computer programming or coding issue and the remote advice that I got from a dealer was along these same lines.
Yes the LIN wire is also yellow in the harness. You could try measureing it with a multimeter while the ignition is on and the engine is running. The voltage from the yellow wire to ground shouldn't be zero or battery voltage but somewhere inbetween. If its stuck at zero you might actually have a break or a bent pin in the connector or something like that between where you measured and the rest of the network. If you see the voltage stuck at battery voltage then its likely that the LIN master is not plugged in or not communicating on the bus for some reason. Again this is specific to the rear seat heating. The front heated seats don't use any LIN between the buttons in the HVAC and the heating control in the seat modules, they're connected by K-CAN.
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      01-20-2022, 02:01 PM   #16
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Same Probelm

Hi Everyone, I'm new to this Thread and have the exact problem with my 2014 X3. Bought it last year with only 27,000 km (Like new) and when the cold hit I found that the driverís side is okay but the front passenger side switch works but the seat doesnít heat. Both back seat switches and seats donít work. I hooked it up to the BMW Vehicle Diagnostic Scanner and got the same 7 codes as mentioned in this post. Iím kind of like everyone else and want to fix this myself rather than paying big bucks to the shop. Iím not an auto electrical engineer and really didnít realize how complicated newer vehicle electronics but I did a lot of research and this is what I can up with.

Iíve also attached some images:

Image #1 shows the wiring to the seats and switches. The ones Iíve marked with the ďRed XĒ show the fault codes that we are all getting. Everything, including the driverís side seat comes from the Junction Box A34/Z1 however there appears to be a T Connector and ďX227í1VĒ which goes to everything that isnít working.


Image #2 shows what all the numbers and lines mean.


Image #3 shows the location in the carís wiring harness where the junction of X227Ē1V is located.


Image #4 shows the location of Junction Box A34 and A34í1B which in the glove box.


Image #5 shows the location of Z1 to Junction Box A34 and A34í1B


Iím not sure why everything after the junction of X227í1V isnít working and whether itís an electronic issue or the physical connection at that junction. Iím not even sure what kind of connection it is. Something has to be going on at that point being the driverís seat works fine and everything on X227í1 doesnít.

I havenít had a chance to see if I could get to the area of the connection of X227í1V to see if thatís the problem.

I may also be in left field on this being I really donít fully understand how LIN components work and link with each other. But with some of you replacing the passenger seat module with no results, it appears that all of the components are in good shape but not communicating for some reason.

Anyway I thought Iíd add this to the post in hopes that we could figure this out and save some money taking it into the shop. It may be a simple thing?
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      01-20-2022, 03:51 PM   #17
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Fantastic, Deano! I'll look for that X227 connector!
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      01-20-2022, 04:55 PM   #18
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awesome good luck!!!
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      01-20-2022, 07:01 PM   #19
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Quote:
Originally Posted by Deano58_BMWX3 View Post
Hi Everyone, I'm new to this Thread and have the exact problem with my 2014 X3. Bought it last year with only 27,000 km (Like new) and when the cold hit I found that the driverís side is okay but the front passenger side switch works but the seat doesnít heat. Both back seat switches and seats donít work. I hooked it up to the BMW Vehicle Diagnostic Scanner and got the same 7 codes as mentioned in this post. Iím kind of like everyone else and want to fix this myself rather than paying big bucks to the shop. Iím not an auto electrical engineer and really didnít realize how complicated newer vehicle electronics but I did a lot of research and this is what I can up with.

Iíve also attached some images:

Image #1 .....
Those are fantastic diagrams, do you have the PDF's they came from? I'm trying to hoard as much technical docs as I can get my hands on since I bought this car a few weeks back
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      01-20-2022, 09:08 PM   #20
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Hey jonmon, I don't have .pdfs for them and just took screen shots when I came across anything dealing with the heated seats.

Here are some of the other links that I had found when I was on my search. Looks like you have the same X3 as me (2014 F25 35i) so these should be good. Not sure if you already have them or not but here's the links anyway.

http://www.bimmerpost.com/goodiesfor...nformation.pdf

https://x3.xbimmers.com/forums/showthread.php?t=803813
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      01-21-2022, 12:51 PM   #21
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Quote:
Originally Posted by Deano58_BMWX3 View Post
Hey jonmon, I don't have .pdfs for them and just took screen shots when I came across anything dealing with the heated seats.

Here are some of the other links that I had found when I was on my search. Looks like you have the same X3 as me (2014 F25 35i) so these should be good. Not sure if you already have them or not but here's the links anyway.

http://www.bimmerpost.com/goodiesfor...nformation.pdf

https://x3.xbimmers.com/forums/showthread.php?t=803813
Thanks, I didn't have the einge one before. Sorry to OP for the minor thread hijack, but here is a dump of the service manual as well in case you don't already have it.

https://bit.ly/3sPMX6H

To the topic at hand, I would strongly suspect that the X227 junction is a splice pack based on the number of branches all marked with the same identifier. But its also possible that it is just wire splices burried in the harness. Doesn't look like an easy location to dig into but the fact that all but one component are working on that bus definitley points to that splice.
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      01-22-2022, 10:49 AM   #22
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Appreciate the link Jonmom, great stuff!!

I agree with you that it appears to be at that X227”1V junction. Like I said before I’m kind of flying by the seat of my pants here and also don’t know anything about the JBE encoded process and whether the encoding of the JBE could impact all of the components that are the same LIN_BUS after the passenger seat.

If the JBE encoding isn’t, or couldn’t, be the issue then it appears to make more sense that the issue is with that X227”1V junction. It’s interesting that some of you had the passenger seat (and assuming it would be the rear seats as well) work and then not work. This would indicate that the X227”1V for some reason connected and then disconnected. Although I don’t know what type of connection it is, it could be something like loose wires, corrosion, or maybe even a wire pinch?.

I bought my X3 last year from the original owner and I’m not even sure if the seats even worked when it came from the dealer. Maybe the wire or harness was slightly pinched at the factory?

Once the weather warms up, (I live in Canada – haha) I’m going to try to see what I can find. Maybe by getting into the area of the harness and just moving it around may re-establish a connection? (if that’s the problem). I also may go to the local wrecker and dig into one of the older X3’s they have on the lot and get to the harness to see what the connections look like.

I have to get to the bottom of this – hahaha!!!!!
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