I unfortunately have fault codes regarding the K-CAN. I can delete them with ICOM A2 ISTA but they immediately show up again like below:
It says “body can” next to FD2 – if I change the language to German it says K-CAN as with the rest of the fault codes.
I have checked the detailed wiring diagram of K-CAN in ISTA (SSP-BTS-SP0000052382) hoping to find a clue.
The Problem is… I just dont get it at all
I am confused that If the ZGM itself reports a K-CAN problem… why are some of the units (on both K-CAN “branches”) not affected while others are?
For E.g. – the CID reports a K-CAN problem. The CID is connected to ZGM via X151*V1 and X151*V2 (high and low).
However – headunit, air condition, head up display share the same lines as above mentioned CID but dont report K-CAN problems at all.
Even more awkward -> the CID is the first unit in the line.
Or the control modules of the rear entertainment monitors (FD1 and FD2) each share the same K-CAN lines as the corresponding seat modules.
The seat modules are allright but FD1 and FD2 report line faults.
I ask help on the forum and some technicians told me the problem could be:
1 Short in cable of K-Bus
2 Broken in cable of K-Bus
3 Fault in gateway ECU
4 Fault in Other ECU on K-Bus
All units must “terminating” the bus with a resistor for correct impedance of the bus.
Note from ISTA doc: Diagnosis of intermittent faults and permanent faults
All cases where a data bus or control unit only fails temporarily (i.e. intermittently) are difficult for diagnosis. In such cases, the entries in the control units’ fault memories do not point unambiguously to an intermittent failure of a particular data bus or control unit.
Intermittent failure of a particular data bus or control unit causes many different fault memory entries in several control units. The system analysis routine processes all of these DTC fault code entries (message missing) for all control units. In this process it employs a probability calculation to localise the fault cause within a specific sector.
If a data bus fails completely and permanently, the affected control units are no longer available for diagnosis. The fault is thus easy to locate.
Another friends think one of the lines would be faulty and the system works in “limp” mode. and communicates on the other line.
common faults are water intrusion somewhere or a cable damage.
check the connection on the affected modules and unplug one by one until the scope pattern on both lines is fine again.
I did have some fault codes regarding low voltage.
But – Im pretty sure I caused them myself by watching TV in the car. No voltage related fault codes since then.
I have not measured the CAN with a Scope yet. I will do the ABL for CAN as soon as I can – Ill report back.
Meanwhile… I did check for fault codes again. Three fault codes (ZGM, VSW and seat module) were just gone. So – there were only four fault codes left(FD1, FD2, TRSVC and CID).
At one point (after clearing all fault codes) there was just one left (TRSVC).