[ewrjontan]

Been light free for a few hundred miles on my 2010 E91 328i (x-drive) with 107,000. Drove to work, then started the car and a bunch of lights were on including:

Traction control
4x4
ABS
e-brake light
seat belt
airbag light

Drove home and car seemed to drive fine. Scanned the car with my Foxwell NT510 and got the following codes. Note, I did an auto scan and cleared everything (had a few DME codes and the transfer box codes), however, these are the codes that persisted and immediately came back. I am assuming only one thing is wrong and causing all of the other codes. I looked all of them up and I don't even know where to begin.

Car Access System CAS
D904 CAS: K-CAN line fault

Driver's side footwell module FRM
E584 FRM: K-CAN Line fault

Integrated automatic heating/air conditioning system IHKA
E704 IHKA control unit K-CAN line fault

Gateway RAD2-GW
E184 CD / M-ASK / CCC / RAD2 / CHAMP-GW: K-CAN line fault

Sliding/tilting sunroof SHD
DA04 SHD: K-CAN line fault

Junction Box electronics JBE 1
C908 JBE: K-CAN line fault

Any help would be appreciated. Literally have had this car for 2 months, one of which was spent down due to maintenance. This car is a nightmare. I love my E36 M3 but this is really making me lose interest in BMWs.

[k90]

Damn.

Most likelly you have one module with failed canbus tranceiver trashing the bus signal. And what you have to do is find the connectors or individual modules that split the branches of K-CAN bus off until the bus recovers. This requires extensive hypertext-based information so I will PM you something to get started or determining if you are up for the task.

EDIT: you should probably start by removing one at a time individual K-CAN stubs/branches from junction box and see if any of them makes a difference.

Ideally you would measure the bus with 2channel oscilloscope to see the waveform to recover. But you can determine with multimeter if canbus L or H signal are ie. shorted to ground. When bus has active modules the bus L and H signals assume ~2.5volt idle state.
When there is activity in the bus:
H signal varies from 2.5V up to 3.5V
L signal varies from 2.5V down to 1.5V

CAN Bus Properties and Troubleshooting:

Note: location and number of terminating resistors in K-CAN is not known(by me at least). So measuring canbus resistance without that information is only good for finding open circuit conditions. You should ofc. see any case maximum of 120ohms.

I would maybe remove IHKA panel and measure from the connector. Seems most accessable point of KCAN.

K-CAN goes everywhere, but to engine bay AFAIK. It's all over the dash and in front footwells, in memory seats, center console. It's in ceiling and trunk too.

Do you have any signs of flooding in your car? Dampness, odours etc.? Sunroof condition? Broken(before bus failure) / leaking? What I have gathered leaking sunroof may flood the car. It's one of thousand ways car can flood ofc. How is the trunk under the covers all nice and dry?

[ewrjontan]

So weird issue, I will add to the thread so others can benefit from this as well.

I checked the voltage of the battery. Directly from the positive and negative terminals on the battery I was getting a reading of 12.01 to 12.03 volts. Mind you the car has been sitting over night and I also had the car on (engine off) last night during my scan.

I also checked from the hidden menu inside of the car and the voltage was reading 11.8 to 11.9 volts. Turned the car on and the voltage was reading 13.8-13.9. From what I am seeing in other threads, the engine on voltage should be a little more than 14v. Does this seem low? The battery is dated April 2020 so it's not old by any means. Could this low voltage be an issue?

I didn't find any wet/damp areas. Also, when I started the car this afternoon, it seems to be running fine and all of the lights are gone... I didn't disconnect a single thing so I am really confused. As mentioned above, I did clear a lot of the codes but a lot of them still came back and should have been present unless they are codes that do not persist. I am sure the issue will present itself again though.

[k90]

It might have hopefully been a rare glitch.. some controller crashing and blocking the bus until power was cycled.

Hmm.. important thing before getting carried away is to check fuses first as ewrjontan suggested in PM. Pro repair guys always check the fuses first.

Unpowered module should not affect canbus physical layer by design. But checking fuses may provide clues if blown fuses are found.

[ewrjontan]

A blown fuse would probably not allow for intermittent lights though right? It would just be on and stay on since a blown fuse is a completely severed connection? I'll have to wait to check them in a couple of days as its supposed to be gross and rainy here until wednesday.

Last night, I had no issues when I left my house for work. Battery read the same (11.9v or so before startup). When I left work, I did notice that the ABS and some other light (I believe DTC/traction control) was on for a hot second and went away.

I will say that since this occurred the first time, I have always turned the car on (without starting the engine), gone into the secret menu to check voltage. Then I press the brake pedal and turn the engine on. The only time I did not do this "start up" process was last night. I am curious if perhaps this could have something to do with me starting the car too fast and there is a delay before recognizing the key or something?

I think I typically get in the car, press the brake pedal, insert the key and press the start button. Maybe I'm being dumb and there is a "proper" order of events? Like, inserting the key first, then pressing the brake pedal, then start button?

[k90]

Originally Posted by ewrjontan

A blown fuse would probably not allow for intermittent lights though right? It would just be on and stay on since a blown fuse is a completely severed connection? I'll have to wait to check them in a couple of days as its supposed to be gross and rainy here until wednesday.

Last night, I had no issues when I left my house for work. Battery read the same (11.9v or so before startup). When I left work, I did notice that the ABS and some other light (I believe DTC/traction control) was on for a hot second and went away.

I will say that since this occurred the first time, I have always turned the car on (without starting the engine), gone into the secret menu to check voltage. Then I press the brake pedal and turn the engine on. The only time I did not do this "start up" process was last night. I am curious if perhaps this could have something to do with me starting the car too fast and there is a delay before recognizing the key or something?

I think I typically get in the car, press the brake pedal, insert the key and press the start button. Maybe I'm being dumb and there is a "proper" order of events? Like, inserting the key first, then pressing the brake pedal, then start button?

Your battery is sitting quite low. Full battery would be 12.6V and voltage drops to 12.2V - 12.4V when ignition is switched on. Lots of short drives + cold temps?

[gunnerxq]

Originally Posted by k90

Your battery is sitting quite low. Full battery would be 12.6V and voltage drops to 12.2V - 12.4V when ignition is switched on. Lots of short drives + cold temps?

+1 I think it's just low battery.