2011 BMW intermittent K-CAN codes

Ray Diagnostician North York, Ontario Posted   Latest   Edited  
Discussion
Network Communications
HVAC
2011 BMW X3 3.0si 3.0L (N52KB30) 6-spd
Erratic Hvac
Over 20 Intermittent K-Can Codes

This BMW sets intermittent K-CAN codes in about 10 modules and in my first capture, CH C shows the green wire K-CAN signal is erratically toggling above ground at the HVAC module and CH D is the yel K-CAN wire at the HVAC. The same K-CAN signals are at the radio.

There are no signs of any water in the trunk but there is a lot of white corrosion in the wire harness under the driver side carpet, caused by water intrusion. 

In the second capture, 

CH A is the grn K-CAN wire at the radio

CH B is the yel K-CAN wire at the radio

CH C is the grn K-CAN wire at the HVAC

CH D is the yel K-CAN wire at the HVAC

I don't think that the last capture is a good K-CAN signal

Someone gave me a good K-CAN waveform and in the last capture, the lower voltage should not be wavy, the lower voltage should be flat at 884mv.

+4
Dmitriy Analyst
Toronto, Ontario
Dmitriy
 

The last capture does not look that bad to me... Here is one description of K-CAN: us​.​autologic​.​com/news/bmw-instr… "K-CAN is a 2-wire system; one wire is K-CAN High, and the other is K-CAN Low. • Use oscilloscope to diagnose K-CAN High and Low patterns. High and Low square wave should mirror each other. A volt meter is only a quick check and not a definitive

+4 Ð Bounty Awarded
Michael Owner/Technician
Cartersville, Georgia
Michael
 

Ray, I think you should look at SI B61 18 14. This is a common problem and would be a good place to start. If you can't find it I can send it to you tomorrow. Good Luck, MIke

+1 Ð Bounty Awarded
Dmitriy Analyst
Toronto, Ontario
Dmitriy
 

Do you refer to this SI? static​.​nhtsa​.​gov/odi/tsbs/2014…​.​pdf It's for K-CAN2, not K-CAN... Is there a similar one for K-CAN?

+1 Ð Bounty Awarded
Justin Technical Support Specialist
Fresno, California
Justin
 

I think its important to mention, to prevent confusion among those that aren't well experienced with BMW. "K CAN" is a CAN Bus only in name, it doesn't follow the standard rules of CAN Bus everyone is generally familiar with. It is essentially 2 single wire K line bus' in which one has been inverted. There is no standard or even documentation of terminating resistors and the value can be 800ohms

+9 Ð Bounty Awarded
Michael Owner/Technician
Cartersville, Georgia
Michael
 

Hi Dmitriy, That bulletin only applies if the faults are K-Bus2 related. I should have paid more attention to the details of the post! Thanks for correcting me! Mike

+1 Ð Bounty Awarded
Justin Technical Support Specialist
Fresno, California
Justin
 

I think its important to mention, to prevent confusion among those that aren't well experienced with BMW. "K CAN" is a CAN Bus only in name, it doesn't follow the standard rules of CAN Bus everyone is generally familiar with. It is essentially 2 single wire K line bus' in which one has been inverted. There is no standard or even documentation of terminating resistors and the value can be 800ohms

+2 Ð Bounty Awarded